O'Brien could refer to:

• Miles O'Brien, transporter chief aboard the USS Enterprise-D, and Chief of Operations aboard Deep Space 9
  • Miles O'Brien (mirror), the mirror universe version, also known as "Smiley"
  • Miles O'Brien (replicant), a replicant created by the Parada government
• Keiko O'Brien, biologist and wife to Miles O'Brien
• Molly O'Brien, first child of Miles and Keiko O'Brien
• Kirayoshi O'Brien, second child of Miles and Keiko O'Brien
• Michael O'Brien, father of Miles O'Brien
• Miranda O'Brien, an alternate timeline descendant of Miles O'Brien
• Sean Aloysius O'Brien, labor union leader in the 20th century, and ancestor to Miles O'Brien
• O'Brien family, the family unit that Miles and Keiko belong to
• O'Brien, a character in the Dixon Hill stories

This is a disambiguation page; that is, one that points to other pages that have the same or a similar name. If you followed a link here, you might want to go back and fix that link to point to the appropriate specific page.