Langdyne

Langdyne is the het ship between Scott Lang and Hope van Dyne from the Marvel Cinematic Universe.

Ant-Man
Following Scott's prison break, he found himself waking up in an unfamiliar place, with Hope standing in front of him. Scott questioned whether Hope had been watching him sleep the whole time, which she confirmed. Hope cited Scott's previous attempt to steal as the reason. Scott was startled when he began to notice the insects crawling all over the floor, with Hope revealing they were giant tropical bullet ants tasked to watch over Scott when she could not. Afterward, she told Scott to meet Pym downstairs and left him.

In the dining room, Hope was trying to convince Pym that Scott's participation was unnecessary for their plan. Scott joined them, with Pym expressing his assumption that Scott had met Hope, which Scott confirmed, calling her 'great'. It turned out that Hope was the one who had Scott arrested for stealing the suit. She was persistent on her doubts of Scott's ability, still wanting to wear the suit instead of him, also disappointed that Hank 'trusted' the criminal more than his own daughter. This led Scott to also doubt his own abilities, however Pym managed to make him overcome his insecurities by comparing their situations, both striving to make their daughters proud of them.

Scott began training with Hope, although Hope was unimpressed with his ability and was very vocal about it, calling him 'princess' and 'useless' due to his failures, and regarded his punches 'terrible'. Lang became covered with bruises and cuts, and Hope was aware of this. In an occasion, Scott was struggling to make the ants listen to him, this made Hope even more unhappy with his incompetence, prompting her to leave.

When Hope was about to leave in her car, Scott got in, blaming her for not locking the doors. Hope questioned Scott's seriousness about the mission and his awareness of the risk, noting he had a daughter. Scott answered that he was doing the mission for his daughter, which led Hope to tell her story with her father following her mother's death. She showed her disappointment about Pym wanting to 'shut her out'. Scott assured Hope that Pym did trust her, also explaining that the only reason he chose Scott to wear the suit instead was to not risk losing her.

The revelation softened Hope a bit. She changed the topic to Scott's daughter, admitting she did not know that he had a daughter when she got him arrested. She asked her name, which later she called pretty. She tried to encourage Scott to clear his mind when trying to move the ants, by remembering his wish to see Cassie. She gave Scott the earpiece to talk to the ants, then placed a coin on the dashboard. Scott succeeded at getting the ants pick up the coin and then spin it, which she complimented.

Scott managed to retrieve the Signal Decoy, but this action was being witnessed by an Avenger, Sam. Hope reassured Scott that he did good and to not mind Pym's remarking his action as irresponsible and dangerous. To carry out the plan that had complicated even more, Scott brought three of his friends, Luis, Dave, and Kurt to Pym's residence. When they fell asleep, Scott tried to thank Hope, which she cut off by mentioning that their actions were intended for a very big purpose. She added that she was glad that Scott 'might have a slight chance' of 'maybe pulling this off'. Scott proceeded to thank her for her talk on the car, and Hope responded by admitting that she had gone from despising him to 'almost liking him'. When Scott encouraged her to write poetry, Hope laughed, suggested him to sleep, and left. They later executed the plan to steal the Yellowjacket.

Following the victory over Cross, Pym revealed that he had been teleported into the Quantum Realm, however he did not remember anything. Though Pym was very eager to know what had happened, he presumed that the human mind just couldn't comprehend the experience, with hopes flourishing in his heart to bring his wife back. When he got out, he found Scott and Hope kissing, asking when did the thing happen. Hope dismissed it and say that nothing was happening, but Scott teased them by saying that something was 'kind of happening'. Scott then feigned his surprise that Hope grabbed and kissed him, which made Hope look at him with disbelief as he quickly left.

Quotes
"I wanted to be his partner. But he said he wants you."

- Cassie to Hope, Ant-Man and the Wasp "I lost someone very important to me."

- Scott about Hope, Avengers: Endgame

Fanon
With the relationship between the two being established at the end of Ant-Man, the ship quickly garnered interest in the fandom. They are the main ship in the Ant-Man and the Wasp Movieverse fandom, as the name implies, though a relatively minor ship in the Marvel Cinematic Universe. Fans like to see the interaction between the two due to their conflicting relationships. Scott makes mistakes or does ridiculous things all the time, meanwhile Hope is a very snarky person who calls him out whenever she gets the chance to. Alhough Hope is very visibly tired of Scott's humour and recklessness, she continues to admire him nonetheless. She can be seen showing her soft side to Scott sometime. It is also interesting that Hope is most of the time more competent than Scott, but this doesn't get in the way of their relationship, as they are very comfortable with each other.