Ludolph van Ceulen (28 January 1540-31 December 1610) was a German mathematician. Born in Hildesheim, Germany, like many Germans during the Catholic Inquisitions, he emigrated to the Netherlands. He moved to Delft to teach fencing and mathematics. In 1594 he opened a fencing school in Leiden. In 1600 he was appointed the first professor of mathematics at the University of Leiden. He died in Leiden. Calculating pi Ludolph van Ceulen spent a major part of his life calculating the numerical value of the mathematical constant pi using essentially the same methods as those employed by Archimedes some two thousand years earlier. He published a 20-decimal value in his 1596 book Van den Circkel ("On the Circle"), later expanding this to 35 decimals. After his death, the "Ludolphine number", 3.14159265358979323846264338327950288..., was engraved on his tombstone in Leiden. The tombstone was later lost but was restored in 2000.

This is from the pi article on Wikipedia. "As early as the 19th century BC, Babylonian mathematicians were using pi = 25/8, which is within 0.5 percent of the exact value. An Egyptian scribe named Ahmes wrote the oldest known text to give an approximate value for pi. The Rhind Mathematical Papyrus dates from the Egyptian Second Intermediate Period, though Ahmes stated that he copied a Middle Kingdom papyrus (i.e. from before 1650 BC) and describes the value in such a way that the result obtained comes out to 256/81 or 3.160. The Indian astronomer Yajnavalkya gave astronomical calculations in the Shatapatha Brahmana (c. 9th century BC) that led to an approximation of pi = 339/108 = 3.1389, which is correct to two decimal places when rounded. In the third century BC, Archimedes showed that 3 + 10/71 < pi < 3 + 1/7, and later formed a proof that 22 over 7 exceeds pi, which was by that time already in usage. The Chinese mathematician Liu Hui in AD 263 computed pi to 3.141014, which is correct to 3 decimal places, though he suggested that 3.14 was a good enough approximation. The Indian mathemetician and astonomer, Aryabhata, in the 5th century gave an accurate approximation for pi. He wrote "Add four to one hundred, multiply by eight and then add sixty-two thousand. The result is approximately the circumference of a circle of diameter twenty thousand. By this rule the relation of the circumference to diameter is given." In other words (4+100)×8 + 62000 is the circumference of a circle with diameter 20000. This provides a value of pi = 62832/20000 = 3.1416, correct when rounded off to 4 decimal places. The Chinese mathematician and astronomer Zu Chongzhi in the 5th century computed pi between 3.1415926 and 3.1415927, which was correct to 7 decimal places. He gave two other approximations of pi: 355/113 and 22/7." There is more to the article, but what appears here should help answer your question. I'm not sure anyone really knows exactly who discovered pi, though. It's been around for a long time - 4,000+ years. http://en.wikipedia.org/wiki/History_of_numerical_approximations_of_%CF%80

We know that the Egyptians and the Babylonians knew about the existence of the constant ratio pi, although they didn't know its value as well as we do today. They had figured out that it was a little bigger than 3; the Babylonians had an approximation of 3 1/8 (3.125), and the Egyptians had a somewhat worse approximation of 4*(8/9)^2 (about 3.160484), which is slightly less accurate and much harder to work with. The modern symbol for pi was first used in 1706 by William Jones, who wrote: "There are various other ways of finding the Lengths or Areas of particular Curve Lines, or Planes, which may very much facilitate the Practice; as for instance, in the Circle, the Diameter is to the Circumference as 1 to (16/5 - 4/239) - 1/3(16/5^3 - 4/239^3) + ... = 3.14159... = "(see A History of Mathematical Notation by Florian Cajori). Pi (rather than some other Greek letter like Alpha or Omega) was chosen as the letter to represent the number 3.141592... because the letter pi in Greek, pronounced like our letter 'p', stands for 'perimeter'.

The ancient egyptians figured out pi to the first 6 digits. With the tools they had back then, that's really good. 3.14159