Reed Edward Diamond (born July 20, 1967) is an American actor. He currently appears in the new NBC series Journeyman as Jack Vasser, the main character's brother.

Personal life
Diamond's early roles included guest starring on Law & Order and Class of '96, and movies such as Memphis Belle (1990) and Clear and Present Danger (1994). His first big break came in 1995 when he joined the cast of Homicide: Life on the Street as Det. Mike Kellerman. That same year, Diamond married Frederika Kesten. They divorced in 1997, after which time Diamond began dating his Homicide co-star Michelle Forbes.
Diamond's character was written out of the series at the end of season six, although he would reprise his role as Kellerman for a two-episode story in the show's subsequent seventh, and final, season. In 2000, a feature length TV movie was produced to wrap up the series, which saw the return of all the major Homicide cast, including Diamond. Recent roles include a re-make of High Noon (2000), Three Days (2001), - which he starred in alongside then-girlfriend Kristin Davis - S.W.A.T. (2003), Spider-Man 2 (2004) and Good Night, and Good Luck. (2005).
As well as playing the recurring role of Stuart Collins on Judging Amy from 1999 to 2003, Diamond has guest starred on Crossing Jordan, The West Wing, Medium, Numb3rs, Stargate SG-1 and Without a Trace. He was also promoted as one of the main cast members of The Shield, appearing as Detective Terry Crowley, so as to surprise viewers when he was murdered at the end of the first episode in 2002. He is currently staring in the new ongoing series Journeyman.