Robert Hugh Trethewey (17 October 1902 – 31 May 1989) was an Australian politician.
He was born in Eaglehawk to mining engine driver Robert Hugh Trethewey and Louise Turnbull.
In 1918 he commenced work for the New Zealand Insurance Company (NZI).
He rose through the ranks of NZI and managed branches in Bendigo (1940–46, 1948–62), Maryborough (1946–48) and Toowoomba (1948).
In 1964 he was elected to the Victorian Legislative Assembly as the Liberal and Country Party member for Bendigo.