Karen Alexandria Kain, CC (born March 28, 1951 in Hamilton, Ontario) is a retired Canadian ballet dancer.

Kain's mother started her in ballet because she believed it would improve her daughter's posture, poise, and discipline. Kain began training at the National Ballet School of Canada in Toronto in 1962. After graduation in 1969, she was invited to join the National Ballet of Canada. She became principal dancer in 1971, dancing central roles in a wide array of ballets, eventually becoming a well-known dancer in Canada.

In 1973, she won silver in the women's competition and another silver for Best pas de Deux (with Frank Augustyn) at the second International ballet competition.

She worked as a guest artist with Roland Petit's Le Ballet National de Marseilles, the Bolshoi Ballet, the London Festival Ballet, the Paris Opera Ballet, the Hamburg Ballet, the Vienna State Opera Ballet, and the Eliot Feld Ballet.

In the late 1970s Kain stopped dancing for a period, but in 1980 resumed dancing with the National Ballet of Canada, where she stayed for a further 15 years. Kain retired from dancing in 1997.

In 1976, she became an Officer of the Order of Canada and was made a Companion of the Order of Canada in 1991. She holds honorary degrees from the University of Toronto, York University, McMaster University, Trent University, and the University of British Columbia. In May of 1998, the French Government named her an Officer of the Order of Arts and Letters. Among Kain's other honours are the Performing Arts Award (1992) and the National Arts Centre Award (1997). In 1996, she became the first Canadian to receive the Cartier Lifetime Achievement Award. The choreographer Marguerite Derricks cited Kain as one of her heroes.

In 1998, Kain returned to the National Ballet of Canada as part of the senior management team, in the role of artistic associate. She supported artistic director James Kudelka against principal dancer Kimberley Glasco in a wrongful dismissal suit. In 2005, she succeeded Kudelka as artistic director.

Kain is the president of the Dancer Transition Resource Centre. In 2004 she was appointed chair of the Canada Council for the Arts. In 2007 Karen Recieved the Barbara Hamilton Memorial Award from the City of Toronto.

Her autobiography, Movement Never Lies, was published in 1996 by McClelland and Stewart. Kain has been married since 1983 to Ross Petty, a stage and film actor, and producer of theatrical pantomime productions in Canada for over 20 years.

Kain's brother, Kevin Kain, is a noted tropical medicine expert based in Toronto, Ontario.