Gillian Ann Sandeman (born c. 1937) is a former politician from Ontario, Canada. She was a New Democratic member of the Legislative Assembly of Ontario from 1975 to 1977. She represented the riding of Peterborough.

Sandeman is a prominent social activist in the Peterborough area, having served as a president of the city's social planning council,^[1] and has written an occasional gardening column for the Peterborough Examiner.^[2]

Sandeman ran as the New Democratic Party candidate for Peterborough in the 1974 federal election, losing to incumbent MP Hugh Faulkner.^[3] In the 1975 provincial election she ran as the NDP candidate in the riding of Peterborough. She defeated Progressive Conservative incumbent John Turner by 505 votes.^[4] Two years later she lost to Turner in a rematch, this time losing by 2,648 votes.^[5] She was the NDP candidate in the 1988 Federal election but lost to PC incumbent Bill Domm.^[6]

In 1978, she considered running in the leadership convention to replace Stephen Lewis but decided against it.^[7] Later that year she became executive director of the Elizabeth Fry Society.^[8] In 1984, she was elected president of the Ontario NDP.^[9] In 1986, at a party convention she defeated Judy Rebick who challenged her position as party president.^[10] In 1988, she became vice-president of the Federal NDP and was a professor at Trent University.^[11]

In 1991 she accepted a position as executive assistant to Education Minister Marion Boyd.^[12] In 1994, she was appointed to the Ontario Parole Board.^[13]