Sir John O'Shanassy, KCMG (18 February 1818 – 5 May 1883), was an Irish-Australian politician who served as the 2nd Premier of Victoria. O'Shanassy was born near Thurles in County Tipperary, Ireland, the son of a surveyor, and came to the Port Phillip District (later Victoria) in 1839. He went into business in Melbourne as a draper, and by 1846 he was rich enough to be elected to the Melbourne City Council and to become the founding chairman of the Colonial Bank of Australasia. By the 1850s he was a major landowner and one of the wealthiest men in the colony. He also became a recognised leader of the large Irish Catholic community.