Upsilon Andromedae b (occasionally referred to as Upsilon Andromedae Ab to distinguish it from the red dwarf star Upsilon Andromedae B) is an extrasolar planet orbiting the Sun-like star Upsilon Andromedae A every 4.62 days. Discovered in 1996 by Geoffrey Marcy and R. Paul Butler, it was one of the first hot Jupiters to be discovered. Upsilon Andromedae b is the innermost known planet in its planetary system.