Robert V. Callahan (born April 11, 1937 in New York City, New York) is a politician in Ontario, Canada. He served as a Liberal member of the Legislative Assembly of Ontario from 1985 to 1995.

Callahan has a Bachelor of Arts degree from the University of Toronto and a law degree from Osgoode Hall at York University. He operated a private legal practice in Toronto from 1965 to 1966, when he joined the firm of Beatty, Bowyer & Greenslade in Brampton. In 1969, he became a partner in the Brampton firm of Cook, Callahan & Leschied (which changed its name to Callahan & Leschied in 1981). Following the departure of Leschied in 1989, he continued in private practice.

Callahan served as an alderman on the Brampton city council from 1969 to 1985, representing Ward 3. He first ran for the Ontario legislature in the 1977 provincial election, but finished third against Progressive Conservative Bill Davis, the sitting Premier, the constituency of Brampton . He challenged Davis again in the 1981 election, and finished a distant second.

Bill Davis retired from the legislature in early 1985, and Callahan was able to win the Brampton seat on his third effort. In the provincial election of 1985, the Progressive Conservatives under Frank Miller were reduced to a minority government as Liberal support increased in much of the province. Callahan defeated PC candidate Jeff Rice in Brampton by over 4,000 votes, and became a backbench supporter of David Peterson's Liberal government after Miller's ministry was defeated in the legislature.

The Liberals won a landslide re-election victory in the 1987 provincial election, and Callahan defeated his nearest opponent by over 11,000 votes in the redistributed riding of Brampton South . He was not appointed to cabinet, and remained in the backbenches.

The New Democratic Party won an unexpected majority government in the 1990 provincial election, and the Liberals were reduced to only 36 MPPs. Callahan was one of these, defeating NDP challenger John Scheer by only 424 votes. In 1992, he was appointed as his party's critic for Correctional Services.

In 1993, Callahan was a vocal opponent of the NDP government's plans to prohibit the picketing of abortion clinics within Ontario.

In the 1995 provincial election, the Progressive Conservative Party under Mike Harris won a majority government based primarily on support from Greater Toronto Area communities such as Brampton. Callahan lost his own seat to PC candidate Tony Clement, later a provincial cabinet minister and a candidate for the leadership of the Conservative Party of Canada.

Callahan returned to municipal politics after his defeat, and was re-elected for Ward 3 on the Brampton City Council in 1997. He is still a council member as of 2005, although following redistribution he now serves as one of two members for "Ward 3 & 4".