For the Australian comedian, see Dave O'Neil. David N. O'Neil (July 23, 1874 - June 9, 1947), also known as Dave O'Neil, was an American businessman and poet of the early 20th century. He was also an occasional stage actor. In 1937, he built an outdoor theatre on his estate in Cos Cob, Connecticut for his family to use, which is known as the O'Neil Outdoor Theatre.