The Old Babylonian Empire was at its height in Mesopotamia between 1900 BC and 1600 BC, long before the Pythagoreans. In 1945, a tablet (now referred to as Plimpton 322) was uncovered at an archeological cite in modern Iran. The tablet, written in cuneiform, is a table separated into 4 columns. What is fascinating about this tablet is that these numbers, which are actually integers, correspond to integers that together form what we call Pythagorean triples. In other words, each of these groups of numbers are integers that when their squares are added together, they form a perfect square. Some of these triples are commonly known, even though people may not realize they are Pythagorean triples. Some common triples are (3,4,5), (5,12,13), (7,24,25) and many more. These are pythagorean triples because 32 + 42 = 9 + 16 = 25 = 52. You can verify the other two.
This tablet suggests that the Babylonian civilization knew about the Pythagorean theorem. While there is no evidence to suggest that they were able to prove such a theorem, there is evidence that they were able to produce a general form to generate Pythagorean triples, something that was widely unknown until Euclid came around a millennium and a half later.