William John Watson (1839 – 18 August 1886) was an Irish-born Australian politician.
He was born at Stone Bridge in County Armagh to farmer James Watson and Sarah McLean.
In 1880 he was elected to the New South Wales Legislative Assembly for Young, but he did not re-contest in 1882.
His narrow victory in 1885 was overturned on appeal and James Mackinnon was installed in his place.
Watson did not return to politics and died in Sydney in 1886.