Lukadrinette

Lukadrinette is the poly ship between Luka Couffaine, Adrien Agreste and Marinette Dupain-Cheng from the Miraculous Ladybug fandom.

Canon
Marinette and Adrien both met Luka on his boat house during the music festival, and while Adrien is Marinette's long held crush, just as Ladybug is Adrien's, Marinette had began to develop feelings for Luka shortly after she met him; who also has a crush on Marinette. Because of this Marinette begins to question her old and new feelings for the two boys, which is why she froze in front of them when they both offered to help Marinette get up from the spot she ended up in when she sild and fell on the ice, as she felt on her end that she has been placed in a position where she might have to decide between the two. When Luka notices that Marinette has feelings for Adrien, he tells her that she should go and talk to him, Marinette thanks Luka for his advice with a kiss before she dashes over to Adrien.

In "Desperada", Marinette's heart faces another struggle between the feelings she has for both boys. As when Adrien walked into the room Luka was teaching Marinette how to play a few notes on his guitar she became worried at what he might be thinking, as Adrien had brought Kagami and had made a foul of herself when she greeted them. A moment later Jagged Stone spots Marinette and ask her if she knows anyone who is a guitarist that can team up with him, despite knowing that Luka is one and has been playing since he was young she recommends Adrien, who is more of a pianist and has little guitar skills. Even though Adrien tells her this and Jagged asks Marinette about Luka, she ends up asking Luka if Adrien could borrow his guitar. When the titled Akumatized villain attacks them, the two boys notice that Ladybug is struggling and go to aid her, until the three are able to get away.

Ladybug thanks them for their help, before reminding them that they did was dangerous as well as brave. She then leaves them to fetch the Snake Miraculous from Master Fu, Ladybug tells Cat Noir that she plans to give it to Adrien, as she doesn't know that her partner and crush are the same person. Since Cat Noir knows that he can't tell Ladybug this, he takes her to the place where he earlier left Luka, as it was also the place where Adrien is purport to be hiding, before they go to find "not", after Cat Noir gets Luka back into his hiding place. After de-transforming and catches up to Ladybug, she hands him the Snake Miraculous and uses it to become Aspik, but after Aspik uses all of his second chances to impress Ladybug while trying to fight Desperada, Adrien takes it off and hands it back to her as he isn't the perfect one for it. Luka on the other hand is and both Ladybug and Adrien agree that the Miraculous should be entrusted to him, as he uses it to become Viperion. Unlike Aspik, Viperion was careful with his powersuper wisely and once he found away for them to defeat Desperada, he uses second chance so he can share his plan with the main duo before they can set it into action.

Season 2
Captain Hardrock
 * The end card is of Marinette blushing, while she is "standing" between Adrien and Luka, who might be looking at each other with a smile.

Frightningale
 * The trio are seen dancing together in a scene from Clara Nightingale's music video, with the two boys wearing a Ladybug mask while Marinette's is of a black Chat Noir mask.

Frozer
 * As Adrien sees Marinette and Luka getting ready to skate together, he goes up to her.
 * When Marinette fell down at the ice rink, both Adrien and Luka officered to help her back up while smiling at her.
 * The three are seen in the end, where Marinette is seen as her civilian and superheroine self.

Quotes
"It's way more complicated."

- All three at the same time in Wishmaker

Fanon
The ship could simply be due to Marinette having romantic feelings for both boys, who are friends of hers and have their own romantic feelings for her. Some have Lukadrinette rival with Adrigaminette (Adrien, Kagami x Marinette), since they both serve as compromise ships.

Some have Adrien view Luka as a love rival for Marinette's affections, once he begins to develop feelings for her alone, consciously or unconsciously. As there have been sighs of Adrien possibly being jealous of Luka or slowly realizing his feelings for Marinette, from when he first saw them together at the rink.

Because the leaks about Marinette, Adrien and Luka's upcoming superhero forms were reveled at the same time, it inspired fans to do fan artwork of Cat Noir, Multimouse (Marinette through the Mouse/Rat Miraculous) and Viperion together; despite knowing that cats and snakes eat mice.

Since the season three episode, "Timetagger", reveals that during the time of their future adulthood, Ladybug and Cat Noir have assembled a team of fellow Miraculous holders, that might have Luka as one of its members.

On AO3, poly the ship has over 46 fanfics.

Fandom
FAN FICTION
 * Marinette/Adrien/Luka on FanFiction.Net
 * Marinette/Adrien/Luka on FanFiction.Net

TUMBLR

Trivia

 * According to Feri González, Luka isn't limited to the role of alternate love interest, the same with Kagami Tsurugi.
 * All three of them are Jagged Stone fans.
 * Adrien had once played the part of keyboard player as a guest member in Luka's band, Kitty Section, while Marinette had designed costumes for the rock band.
 * Even though Adrien wasn't playing with them during that time.
 * Luka's younger twin sister, Juleka is one of Marinette and Adrien's classmates.
 * The out of order released episode "Party Crasher" reveals that sometime before the events of it, Luka will become one of Ladybug and Cat Noir's occasionally allies whenever he is given the Snake Miraculous so he could help them as the snake-themed superhero, Viperion.
 * Even though fans knew for sometime that Luka would one day receive the Snake Miraculous, from concept art leaks that revel Luka's superhero title, form and weapon; as well as the forms and titles that Marinette and Adrien would go by from using the other Miraculouses on themselves in the future.

Variations

 * Adrienette refers to the ship between Adrien and Marinette
 * Lukadrien refers to the ship between Luka and Adrien
 * Lukanette refers to the ship between Luka and Marinette