according to wikipedia – Both.

According to my calculus teachers; both.

i hate both of them for doing so

http://en.wikipedia.org/wiki/Newton_v._Leibniz_calculus_controversy

I side with Leibniz because he published first and Newton was a jerk.

Newton and Leibniz both created Calculus, but did so independently—they were bitter rivals—and did so while trying to solve very different problems. Newton was doing physics and Leibniz was studying limits.

Newton had practical uses for it… so I side with him.

I can also pronounce his name :P

Oh boy… you’re opening up a can of worms here. I think the general consensus is that they both did it independently. But Newton was a son of a bitch about it, and more or less devoted the rest of his life to tearing down Leibniz.

Leibniz has one thing going for him – his notation was more useful and flexible, and is the one we mostly use today (i.e. df/dx for a derivative. Newton put dots above a variable to indicate derivatives)

Leibniz had at one time, prior to Newton’s publication of his work, met Newton, discussed the concepts involved and, some say, saw preliminary notes. However, Newton’s calculus was concerned entirely with change with respect to time, since mechanics (laws of motion) were his principle interest. Some classical mechanics teachers and texts still use Newton’s “dot” notation where a variable with a single dot above it represents the first derivative of that variable with respect to time, two dots the second derivative, etc.

Leibniz, whose notation is commonly used today, considered change of one variable (dependent) with respect to another variable (independent). For instance, with pressure of an enclosed gas expressed as a function of temperature, the rate of change of pressure with respect to temperature could be determined at any point (with the usual provisos of continuity and continuous differentiability).

Leibniz was also very involved in philosophy/theology, having an ongoing discussion (through publication) with Spinoza. Experts have concluded that Newton and Leibniz invented (discovered) the calculus independently.