U-434 may refer to:
- German submarine U-434, Type VII submarine launched in 1941; sunk in 1941 on her first patrol
- Soviet submarine B-515, (now known as U-434), a Tango-class submarine built in 1976; currently a museum ship in Hamburg
This article includes a list of ships with the same or similar names. If an internal link for a specific ship led you here, you may wish to change the link to point directly to the intended ship article, if one exists.