Five kings of Jerusalem bore this name. The first Baldwin was also the first king of Jerusalem during the first Crusade. Baldwin II was the third king, and Baldwin III was the uncle of Baldwin IV, the Leper King who ruled Jerusalem from 1174 to 1185. Baldwin V, a child, succeeded him, but he died shortly before Jerusalem fell.
John Baldwin is a rather famous bearer of this name. He played bass, as well as a few other instruments on occasion, for a rather famous 70's band called Led Zeppelin. He is better known by his stage name of John Paul Jones.