Leslie Lewis Dan (born November 26, 1929) is a Canadian businessman and philanthropist.

Born in Budapest, Dan can to Canada after World War II in 1947. He survived during the war by using false identity papers. He graduated with a BSc from the University of Toronto School of Pharmacy in 1954. He completed his MBA in 1959. In 1960, he started a company which distributed over-the-counter drugs.

In 1965 he started Novopharm . When he sold the company in 2000, to Israel's Teva Pharmaceuticals for an estimated $430 million, it had sales of $750 million and it employed 3,000 people. He then started a new company, Viventia [formerly Novopharm Biotech], which specializes in the discovery and development of products for the treatment of cancer. He currently is the Chairman.

In 2003, he had an estimated net worth of $1.26 billion.

A notable philanthropist, some of his donations and honours include:

• He donated $15 million to the University of Toronto.
• The University of Toronto Leslie Dan Faculty of Pharmacy is named in his honour.
• The new University of Toronto Leslie L. Dan Pharmacy Building, designed by Sir Norman Foster and to be completed in 2005, is named in his honour.
• He founded the Canadian Medicine Aid Programme (CAN-MAP) in 1985, an organization which provides life saving medicines and other aid to the sick in the Third World.
• In 1996 he was made a Member of the Order of Canada and awarded the Order of Ontario.
• He received an honorary Doctorate of Laws Degree from Dalhousie University in 1996 and the University of British Columbia in 1995.
• In 1997 he received the Distinguished Business Alumnus Award by the University of Toronto Joseph L. Rotman Faculty of Management.
• The Aish HaTorah's Dan Family Building is named in his honour.
• He has donated to Yad Vashem.

He married Judith in 1958. She died in 1995. They had a son Aubrey. He remarried Anna in 1996.