When this is over don’t remember this moment, remember the other ones. New Years Eve, champagne - your terrible, terrible guitar playing that never really got any better even though I said it did. And remember - I had over a century of pain and loneliness before I found you and then three glorious years of love. I love you.
Their relationship began in Total Eclipse of the Heart, when Enzo, who was working with Damon to track down the remaining Augustine members, decided that the best way to get Bonnie to help them find Wes was to threaten her boyfriend, Jeremy, with death. This set their relationship off to a rocky and antagonistic start, but they were ultimately able to set aside their dislike of each other to focus on bringing Enzo and many of Bonnie's friends back from the Other Side before its collapse.
In Season Seven, we see the pair in a romantic relationship, but in a flash forward, after Bonnie gets in trouble with the Armory, three years ago, and Enzo stepped up to keep them away from her. Enzo moves Bonnie up in a cabin, and over the years the two began to grow close. Two years later, after their romantic feelings had build up, the two started a romantic relationship and fell in love. After dating for three years however, they are currently separated due to the Armory's Monster mentally incapacitating him to do the creature's biding (along with Bonnie and Enzo's best friend, Damon). Bonnie, along with their friends, are currently trying to find and save Enzo and Damon from their mental hijacking by the Armory's unknown and mysterious creature.
They are known as "Bonenzo" or "Benzo" (unofficially) by fans.
Throughout The Vampire Diaries Series
Bonnie first met Enzo in Season 5's Total Eclipse of the Heart, when Enzo and Damon revealed their intention to find and kill Wes in revenge for the torture he and the Augustine Society put them through. Since Bonnie was no longer a witch, Enzo, with Damon's support, captured Jeremy and threatened to kill him if Bonnie didn't find a witch to do a locator spell before midnight that night. Though Bonnie was able to find Wes' location with the help of a witch named Liv, Enzo still tried to kill Jeremy by smothering him by forcing a plastic bag over his head. Fortunately, Katherine (who had been secretly pretending to be Elena after performing the Passenger spell to take over her body) reluctantly gave Jeremy CPR and saved his life to maintain her cover.
In Man on Fire, Bonnie, Stefan and Elena were studying together at the bar where Liv works when Enzo arrived, intent on finding out what had really happen to his love, Maggie, whom he had just learned had been killed by a vampire in 1960. Under the impression that Stefan had killed her, Enzo tied up Elena and Stefan and took Bonnie's cell phone to call Damon and have him come over with Stefan's diaries to confirm that he killed her. Enzo then threatened Bonnie's life, wondering aloud if Bonnie could even die, since she technically became a corporeal ghost when she assumed the role of Anchor to the Other Side, so Stefan confessed to killing Maggie to protect her, despite the fact that he didn't actually kill her.
Later, after learning it had really been Damon who killed Maggie, Enzo attacked Liv, causing Bonnie to run over to her to check on her. He then fought with Stefan, and when Stefan grabbed Enzo's heart to scare him into leaving town, Enzo killed himself by forcing Stefan to pull his heart out, knowing that his death would put a huge strain on Stefan's relationship with Damon. Enzo's spirit appeared to Bonnie before he passed through her to the Other Side, and he took great offense when he realized that Bonnie was going to keep Enzo's death a secret from Damon.
In Promised Land, an annoyed Bonnie went to the boarding house to see Damon and complained that, because Damon had promised to bring Enzo back to life, Enzo wouldn't stop bothering her about it. Damon, under the mistaken belief that Bonnie had a way to bring herself back from the Other Side, instructed Bonnie to just add Enzo's resurrection to the spell as well. Later on, Enzo overheard Bonnie admitting to Caroline that there was no way to bring her back from the Other Side and he became so enraged that he knocked down several of the packed up boxes in Bonnie's dorm room.
Bonnie insisted that Enzo needed to accept the fact that he wasn't coming back, but Enzo reminded her of all his years of torture while in captivity, and insisted that he wouldn't be giving up until oblivion took him. The two eventually came up with a plan to bring themselves back to life that involved the help of one of the Travelers who had recently died, Maria, who knew the spell the Travelers used to resurrect Markos. Unfortunately, before they could plan further, Maria was sucked into oblivion. Just as Enzo arrived back to Bonnie to inform her of Maria's demise, Stefan's spirit arrived in front of Bonnie after having just been killed by Julian. Enzo was stunned as he watched Bonnie inform Stefan that they had lost their contact to help them with the spell to bring themselves back to life.
In Home, Enzo appeared during Bonnie and Damon's argument and revealed to Bonnie that he found another Traveler who was willing to teach them the spell in exchange for also being resurrected, and instructed her to call Liv. Finally, though the majority of the Mystic Falls Gang had returned to their hometown, Bonnie was still with Enzo at Whitmore, working on their plan, when Luke's spirit appeared and passed through Bonnie. Enzo became nervous about the growing list of people who were supposed to be resurrected and argued that they shouldn't bring Luke back, too, but Bonnie insisted that they had to keep their promises. Tyler's spirit arrived in front of Bonnie after Markos had killed the Traveler possessing him, Julian, by throwing them into the magic-free-zone, but Bonnie again promised him that she would bring him back, much to Enzo's dismay. As the two were about to head back to Mystic Falls, Silas appeared and revealed himself to be the Traveler who Enzo found to teach them the spell. Bonnie, still furious that he had killed her father, reluctantly agreed to work with him and acted as the middle man to help teach Liv the spell. However, right before they were about to begin, the wind on the Other Side picked up, and started to pull Silas and Enzo into oblivion. While Bonnie managed to save Enzo, she let go of Silas at the last moment in retribution for the terrible things he had done, and he was sucked into the unknown. Finally, once Liv started the spell, Enzo was one of the first people to return to the living world through Bonnie; Bonnie, on the other hand, along with Damon, ended up being trapped on the Other Side just before it imploded, sending them both to a yet-unknown dimension.
In I'll Wed You in the Golden Summertime, Enzo is seen knocking at the door of the Salvatore boarding house. Bonnie is the one who answers the door only to close it immediately when she sees him. He holds it open and explains that he's there to visit Lily who must be lonely and hungry. When Bonnie refuses to let him in, he gives her an iPod, asking her to give it to Lily and telling her that it contains loads of songs from the last era she knew.
The flash forward in Live Through This shows in 2016, Bonnie is living in a mental institution, and is seeking help in a group. When she returns to her room she finds Enzo waiting for her. He tells her that things have gotten bad and that she can no longer hide in away forever. They then kiss, confirming that the two have a romantic relationship in the future. Meanwhile in the present day Bonnie and Enzo have a very antagonistic relationship that consist of bickering and snarky comments.
In Best Served Cold, Bonnie and Enzo arrive at the Salvatore boarding house for Lily Salvatore's dinner mixer. Bonnie sees Enzo and asked "Did whatever animal their serving for dinner get a plus one?" To which Enzo replied that he was invited. Bonnie of course assumes he's there to scope out the competition and he tells her there's no competition to scoop. While they both wait for someone to answer the door, Enzo says to Bonnie that "If anyone was wondering you're my date." to which Bonnie replies "Sorry?"
Later in the episode Enzo sees Bonnie standing across the room and he walks over to her. Bonnie then tells Enzo to have some dignity, he respond to her by telling Bonnie what he overheard Julian telling Beau and proceeds to tell her his plan. Bonnie sees Lily looking over at them, she begins fixing Enzo's tie to make Lily jealous. A confused but yet pleased Enzo asked Bonnie what she was doing. She tells him Lily is looking over here and she's making her jealous like a good date. Enzo starts getting flustered by Bonnie's assertiveness and slightly he steps back from her with a small smile on his face and tells her he got what he came for, bids her a good night; leaving a blushing Bonnie alone, who was quite pleased with herself.
In Mommie Dearest, Bonnie and Enzo go to an impound lot to find Oscar's car, while they are there Bonnie is wondering why Julian would want anything from an impound lot in the first place, Enzo tells her if Julian wants it, he wants it. Bonnie finally understand why Enzo was helping, he doesn't want to help stop Julian he just wants Lily. Enzo informs her that she has unlocked every man's true motivation in life. Bonnie tells Enzo to stop treating Lily like a prize to be won and makes it clear that fighting over a woman isn't the turn on Enzo thinks it is, and that he should try flowers, dinner, and listening. Enzo chuckles at Bonnie's statement. Bonnie then finds Oscar's car, they search the trunk of it to find a small sword. Enzo is ready to take it and kill Julian, meanwhile Bonnie wants to do research on the sword, to see if Julian wants to kill someone with it or is afraid to be killed by it. Enzo brushes her off wanting to just rush in and use the sword on Julian so he can have Lily, Bonnie sarcastically tells Enzo to go pick a fight with an extremely power vampire, that should work out great. Enzo being amused asked Bonnie if she was concerned for him, she shoves the sword to his chest and telling Enzo, he and Julian can kill each other it's a win/win for her.
Bonnie is later seen sitting alone at a table after being told off on the phone by Matt for ditching his calls to hang out with the guy who kidnapped her roommate. Enzo walks over to her with two drinks and takes a seat. He looks to see her dejected face and gives her one of his drinks noticing she had a rough day like him, Bonnie tells Enzo she heard what happened, he responds "with the sword or with Lily, because the answer is the same" Bonnie wants to know if Enzo was giving up on Lily. He tells her "when nine Russians tells you, you're drunk you lie down," he also states that Lily made her intentions clear, Bonnie tells Enzo he's better off without Lily.
In Postcards from the Edge, Enzo saves Bonnie from the huntress (in old age) right on time, who was choking her with her strength. Bonnie asked where he was, he thought she missed him as she said she was wondering where he was. Enzo assumes Bonnie was lying, he does tell her that Matt called in the armory on him, but it didn't turn out the way he expected. Enzo asked Bonnie to help get Rayna's body out and for her to do a cloaking spell. Bonnie leaves Enzo with Rayna to get Nora and Mary Louise, when they return Enzo and Rayna's corpse are gone.
In This Woman's Work, Enzo called Damon's phone because Bonnie didn't answer his phone calls to her. He asked him to get her on the phone but she refused to talk to him because he took the huntress' body, she felt that he has betrayed her trust by stealing Rayna's dead body and then ditching her.
In Moonlight on the Bayou, Enzo calls Bonnie and Damon to the armory because they have a plan to capture Rayna Cruz and lock her back up. Enzo tells Damon and Bonnie how he got involved with the armory, and asked for their help. The duo agreed to help Enzo and the armory take in Rayna. Alone, Enzo tells Bonnie why he's so desperate to find out about his real family. Damon returns telling Bonnie they are leaving since he got info that the armory are shady people. With that Enzo shoots Damon and locks him up with Tyler, then knocks Bonnie and injected her with something to put her on magical timeout. Bonnie tries to rescue Damon from Tyler, she and Enzo get into a huge fight, leading Enzo to reveal that he wanted what Damon has, Bonnie then knocks Enzo out and then cut off his hand to save Damon from Tyler.
In I Would for You, Enzo calls Bonnie to come back to the armory to work together to capture Rayna Cruz. Bonnie shows up and notice Enzo's hand had been put back on. They bicker for moment until Alex St. John appears and tells Bonnie she wanted her to come back. Alex reveals the truth about the shamans and Rayna Cruz's linked to their lives. Enzo stays with Bonnie in the room with the everlasting, Bonnie text Damon the details of what she found out, another Everlasting dies and Enzo reveals to Bonnie if Rayna's last life dies so does Stefan. Bonnie looks for a way to help Damon, Enzo tells her the armory will handle it, but Bonnie didn't think they'd get there in time, and Enzo tells her she had no idea what Damon was planning, hinting that Enzo already knew Damon was going to lock himself away in the coffin until Bonnie dies.
In Days of Future Past, Enzo is told by Nora that the pills made from Rayna's blood that he had been giving to Bonnie were poisonous to witches and teams up with her to get the cure from Alex. Together he and Nora lure Alex to Houston and Enzo discovers that Alex didn't know how to fix it and that Alex somehow knew that he had been stealing from the Armory's supply and giving them to Bonnie.
In One Way or Another, Enzo reunites himself with Bonnie once again, after awhile. They share a romantic moment and then discuss how they plan on handling the Armory looking for Bonnie and the introduction of a relative to members of the Armory, Virginia St. John. Enzo then reveals to Bonnie that the pills she is taking to stay under the Armory's radar are slowly poisoning her. Bonnie becomes worried as Enzo continues to comfort her, but this moment is shortlived when Damon walks in on them after not seeing them for three years.
In Somebody That I Used to Know, this episode shows the development of Bonnie and Enzo's alliance bloom into romance. Enzo and Bonnie are shown to be on the run together for three years, from the Armory. The two bond as they spend their time together trying to stay out of the Armory's radar. In present time, they work together to stop Bonnie from dying. With Damon, they ally with Rayna Cruz to kill all of her marked vampires in exchange for Rayna's last life so that Bonnie could live.
In Kill 'Em All, Enzo and Damon continue to kill vampires on Rayna's hitlist to try and save Bonnie's life. After Enzo grows frustrated as time runs out for Bonnie, Damon and his friends help with Rayna's vampire-hitlist situation as Enzo goes to spend his last moments with Bonnie. However, Rayna successfully gives her last life over to Bonnie, which holds a significant consequence: Bonni will continue Rayna's mission to kill all vampires.
In Requiem for a Dream, Enzo and Bonnie are first seen at the beginning of the episode inside the fireplace room Salvatore Boarding House. Enzo is seen holding Bonnie on his lap as she lies unconscious. Enzo worriedly looks at her face as he and Damon discuss how to get through to Bonnie's Huntress side as she goes through hell in her mind. Caroline and Enzo debate on who should get inside Bonnie's head, but Enzo allows Caroline to go first being she knew Bonnie for years. When Caroline fails to get through to Bonnie and is marked as Bonnie's first target, Enzo immediately emerges himself into Bonnie's head. They shared a compassionate reunion and Bonnie asks him to end her life, Enzo argues with her until her Huntress side comes out and stakes him. Enzo is forced out of Bonnie's head and becomes Bonnie's second vampire target. Enzo decides to stick around despite being marked by Bonnie until she wakes up.
In Gods and Monsters, Enzo attempts to use Bonnie's huntress side in drawing her away from their friends. When Bonnie finally finds Enzo, they share a moment together before Bonnie attempts to kill Enzo, despite her constant fighting in not trying to hunt and kill him. They share a heartfelt goodbye scene together, even saying "I love you" to each other for the last time. However, Damon ends up torching the last corpse that links Bonnie to her huntress side and they are both free from the Hunter's Curse. They share a passionate kiss when they realize they are free from the Huntress Spirit. Unfortunately, shortly after they are reunited, Enzo is mentally manipulated into becoming an emotionless killer, along with Damon. Due to this, Bonnie is forced to try and track Enzo and Damon down and she finds out along with her friends that Damon and Enzo are the ones responsible for the killings across the country. Bonnie, along with Stefan, figure that the creature from the Armory's vault was the one who influenced Enzo and Damon to be emotionless killers.
Enzo: There's always a solution. Your boyfriend came back from the dead; Markos came back from the dead; you came back from the dead!
Bonnie: The travelers used doppelgänger blood in that spell to bring Markos back, which means, they basically destroyed the magic that holds the other side together. It's unraveling and there's nothing anyone can do to stop it. It's over, Enzo. You're not coming back. Accept it.
Enzo: I will accept it when that darkness comes and yanks me to oblivion. I will accept it when I no longer exist. I spent over 50 years stuck in a cell; poked, prodded, tortured. By all rights, I had no hope of ever getting out, but I clung to it. So, I will accept it when it's done... not a minute prior.
Michael Malarkey has shown interest in Bonenzo early this year, when Kat Graham had announced Bonnie would be getting a new love interest due to Jeremy leaving.
The idea for a Bonnie/Enzo pairing began in I'll Wed You in the Golden Summertime when Enzo came to visit Lily at the Salvatore Mansion, where he was met at the door by Bonnie. “Kat [Graham] and Michael [Malarkey] had such … chemistry in that really short scene,” Dries recalls. “We were like, ‘Huh … Let’s explore that relationship.’ Of course, they have no reason to like each other; in the present day, we’ve been telling their hate story. So the whole point is that, when you see them in the future, you’re supposed to be like, ‘Wait, how did they get to there?’ Hopefully it created enough intrigue to keep [fans] guessing.”
Plec promises fans will get to see how Bonnie and Enzo ended up in love over the missing three years, calling their relationship “lovely” and “beautiful.” This story was explored in Somebody That I Used to Know.
Julie Plec on Bonnie and Enzo: "In the case of Bonnie and Enzo, we decided to show them in love with each other as a surprise flash-forward, leaving the audience to wonder how in the hell that happened. I really love the idea of them together. Enzo has so much love to give, but has been constantly disappointed by people in his life. Bonnie, always giving so much of herself to others, deserves the kind of love that is unconditional and powerful and selfless. I love them together." 
Chris Grismer had the Billie Holiday song play out loud for the whole cast and crew while Kat and Michael danced. Everyone was so moved. One of the crew members came up to Holly Brix with tears in her eyes. She wanted Holly to know how much she loved seeing Bonnie get a epic love story.