What was Pixar's first feature film?

While Disney and Don Bluth were duking it out with hand-drawn masterpieces like "Beauty and the Beast" and "The Land Before Time," a bunch of computer nerds in Northern California had a totally different idea. These former Lucasfilm employees thought they could make an entire movie using just computers, and Steve Jobs poured $10 million into a newly-created Pixar to see if they were right. What was the first film they released in theaters?