Who invented the hour hand on a clock?

It's hard to say. Clocks have been around for a couple of thousand years, going back to the Ancient Egyptians, who invented the water clock around 1400 B.C., or even earlier to 3500 B.C. to the invention of the sundial. I suppose the hour hand on a clock was invented in 1510 by Peter Henlein of Germany, whose spring-powered clock, though pitifully imprecise, was an important precursor to invention of the pendulum-powered clock, which included both a minute hand and an hour hand.