Louis Siminovitch CC OOnt FRS FRSC (May 1, 1920 – April 6, 2021) was a Canadian molecular biologist.

[1] He won a scholarship in chemistry to McGill University, earning a doctorate in 1944.

He helped establish the Department of Genetics at the Hospital for Sick Children as geneticist in chief, where he worked from 1970 to 1985.

[3] He was the author or coauthor, at last count, of over 147 scientific papers, reviews, and articles in journals and books.

The annual Elinore & Lou Siminovitch Prize in Theatre is named in his and his wife's honour.