Who invented the first computer?

That really depends on the definition of a "computer". The usual story that computer scientists learn in their introductions is Charles Babbage, who devised a "Difference Machine" to count polynomials, which however, was not yet constructed in his time.

Another "first" was Konrad Zuse's finished in 1938, which was the first programmable computer.

Charles Babbage invented the first computer in in 1822