Because the clock as we know it has been around for thousands of years it is hard to say exactly who invented it. Modern historical debate cannot even narrow it down to a single civilization.
Part of this problem is the lack of information about some ancient civilizations and some is in the definition of the word clock. The identity of the most primitive clock may be a surprise to you. It was something that you and everyone else is very familiar with. It was the sun.
For countless centuries the sun has been used to tell time. When it is directly above us it is noon, when it is on the horizon it is late evening or early morning depending on the direction east or west.
The sundial was developed approximately 5500 years ago as a way of telling time by the sun and it can be considered the most primitive clock. To make a sundial you place a stick upright in a sunny place. The angle of its shadow will tell you the time. Many gardens still have what can be very ornate sundials in them today.
The next revolution in the clock came around 1400BC with the ancient Egyptians who would measure the flow of time with water. They would have two containers one higher than the other and the rate the water would flow from one to the other would measure time spent. This idea was soon very popular and was in used in classical Greece. These are some of the early forms of clocks. The clock as we know it today did not appear until around the 1500 century when the first mechanical clock was built. It was not very accurate however and many advances have been made since.