Ultron's release depends on the context you mean:

• In movies, Ultron was first introduced in the Marvel Cinematic Universe in "Avengers: Age of Ultron," which premiered on April 13, 2015, and was widely released in the U.S. on May 1, 2015.
• In the video game "Marvel Rivals," Ultron was released as a playable character on May 30, 2025, coinciding with the start of Season 2.5 of the game. The game's servers were taken down for maintenance before his release, and after that, players could access the new content.

If you were asking about the film release, it came out in 2015. If you refer to the character's release in the Marvel Rivals game, it was on May 30, 2025.