Scott Edward Harris Lang is a former convicted thief who was struggling to pay child support to his estranged wife for visitation rights to his daughter, Cassie Lang. With the promise of money, he was convinced by Hank Pym to take on the mantle of Ant-Man: a superhero with an advanced suit designed to shrink its wearer to a tiny size while increasing one's toughness, agility, and physical strength. Trained under both Hank and his daughter Hope van Dyne, Lang was to help foil Hank's former protege Darren Cross, who was intending to sell his Yellowjacket Suit design and his copy of the Pym Particles formula to HYDRA and the Ten Rings. However, their plan was discovered by Cross, culminating in a final fight between Cross and Ant-Man. To defeat Cross, Lang had to shrink small enough to enter Cross' Yellowjacket suit and destroy it, sending Lang to the Quantum Realm, but Lang was able to escape. Lang's heroism helped restore his relationship with Cassie and his ex-wife, as well as find a new romantic one with Hope. Lang soon learned that the Avengers were seeking to recruit him.
Against Hank and Hope's wishes, Lang joined Captain America's side during the Avengers Civil War, having been recommended by the Falcon following their previous encounter at the New Avengers Facility, and being informed of Helmut Zemo's plan to awaken the Winter Soldiers. Ant-Man fought against Iron Man and his allies, demonstrating his suit's new ability to enlarge his body to a gigantic size, and allowing Captain America and Winter Soldier to escape and find Zemo. Ant-Man and several of his new allies were then arrested by Thaddeus Ross, who had them imprisoned in the Raft for breaking the Sokovia Accords. When Captain America arrived to free them, Ant-Man and Hawkeye chose not to escape, instead making a deal with the FBI to be put under house arrest so that they could still spend time with their own families.
Three days before Lang could finish his sentence, he had a strange vision of Janet van Dyne, who had remained trapped inside the Quantum Realm, and with whom Lang became psychically entangled with when he was there. This resulted in Lang being kidnapped by Hank and Hope, who had built a Quantum Tunnel machine and intended to use it and Lang to rescue Janet. These plans went awry when Lang and Hope (who had become the new "Wasp") were confronted by both Ghost and Sonny Burch, who wanted to steal the Quantum Tunnel machine for their own selfish reasons. Lang, Hope, and Hank eventually succeeded in rescuing Janet from the Quantum Realm, and Lang was able to return home to finish his house arrest, narrowly avoiding an extended prison sentence.
However, during a trip to the Quantum Realm to gather quantum particles for Ghost, Lang became trapped as Hank Pym's entire family was turned to dust by Thanos following the Snap, along with half of all life in the universe. Lang was unable to escape until 2023, where he regrouped with the Avengers and suggested that they use the Quantum Realm as a means of time travel to undo Thanos' actions. Ant-Man then participated in the Time Heist, where he and the Avengers successfully managed to find and collect the six Infinity Stones from the past and resurrect all life killed by Thanos. However, a past version of Thanos had managed to follow the Avengers through time, and Ant-Man would fight in the resulting Battle of Earth. Thanos and his army were eventually destroyed, after which Lang celebrated the victory with Hope and Cassie, and attended Tony Stark's funeral.