Joan Diamond is a recurring character on FOX drama soap Beverly Hills, 90210. She is portrayed by Julie Parrish.
Joan owns a lamp store and used to work as an actor. She met Nat Bussichio twenty-five years earlier, when they worked on a Roger Corman movie together and were romantically involved. They lived together for a while before being pulled apart by Nat's parents because he was Catholic and she was Jewish.
Steve Sanders takes it upon himself to set Joan and Nat up and try to reignite the flame between them. They date, but break up a couple of months later, citing that they couldn't recapture the past. Clare Arnold and Susan Keats attempt to get them back together, enlisting Steve Sanders and Brandon Walsh for a triple date with Nat and Joan to rekindle the flame. The plan works when Nat and Joan visit their old home. Nat takes Joan in his arms and kisses her.
They are very happy together and have fun until Joan discovers she's pregnant. Nat reacts shocked, but decides that they should get married and tells Brandon, without letting Joan in on the decision, which she seems to take okay. Joan and Nat have the ceremony at the beach, but Joan's water breaks and they marry in the hospital just before Joan gives birth to their son, Frankie, in September 1996.