Otto Julius Klotz OLS, DLS, DTS (March 31, 1852 – December 28, 1923) was a Canadian astronomer and Dominion Surveyor.

He was born in Preston (Cambridge), Canada West, the son of Otto Klotz and Elise (Elizabeth) Wilhelm.

He worked on the British Columbia Railway Belt Survey from 1885 to 1890 and was assigned the task of resolving the United States and Canada boundary dispute during the 1890s.

While in London, England, 1898, he discovered a significant cache of Foreign Office correspondence, much of which pertained to the North American Boundary Commission, some of whose Royal Engineer members were photographers.

His other claims to fame include overseeing the All Red Cable Route connecting Australia and Canada in 1902, and he has been called the father of the Public Library in Ottawa University Club.