Robert Stanley Weir was born on November 15, 1856, in Hamilton, Ontario.

He was a judge, writer, and poet, famous for writing the English lyrics to "O Canada," the national anthem of Canada. Weir attended McGill Normal School, and at the age of 19, he was appointed principal of Sherbrooke Street School, one of the largest Montreal public schools. He graduated from McGill University (B.C.L, 1880; D.C.L, 1897) and began practicing law in Montreal, focusing on the municipal questions. In 1898, he was one of the advocates appointed to revise the charter of the City of Montreal. In 1899, he was appointed Recorder for Montreal. Weir also taught liturgics and jurisprudence in the Congregational College of Canada, affiliated with McGill University. He later served as a municipal court judge and was considered an expert on the historical aspects of municipal law. In 1908, Weir wrote English lyrics for "O Canada" while at his summer home in Cedarville to honour the 300th anniversary of the founding of Quebec City. He served as Vice-President of the Parks & Playgrounds Association in 1922. In 1923, he was elected a Fellow of the Royal Society of Canada. In 1926, he was appointed a judge for the Exchequer Court of Canada.

In 1882, he married Margaret Alexander Douglas (1863–1933). He died on August 20, 1926, in Cedarville, Lac Memphremagog, Quebec.