Ian Robert Cathie (born 24 October 1932) is a former Australian politician.
Born in Melbourne to printer George Mitchell Cathie and Sybil Balding, he attended state schools, Wesley College, then the University of Melbourne, where he studied teaching. On 5 January 1957 he married Christine Watson, with whom he had four children; he married again on 3 July 1976 Jean Germain, an industrial nurse. He was president of the Peninsula Victorian Teachers Union in 1959 and taught at Frankston and Mordialloc-Chelsea High Schools, as well as serving on the council of Monash University from 1977 to 1982.
In 1964 he was elected to the Victorian Legislative Council as a Labor member for South Eastern Province; he was defeated in 1970, but in 1976 was elected to the Legislative Assembly seat of Carrum, which he held until 1988. Ministerial appointments under the John Cain (Jnr) government include:
From 1994-1997 he was a Commissioner of the City of Greater Dandenong. In 2010 he was elected President of Glen Eira University of the Third Age (U3A).