Viscount Weir, of Eastwood in the County of Renfrew, is a title in the Peerage of the United Kingdom. It was created on 25 June 1938 for the Scottish businessman, public servant, politician and former President of the Air Council, William Weir, 1st Baron Weir. He had already been created Baron Weir, of Eastwood in the County of Renfrew, on 26 June 1918, also in the Peerage of the United Kingdom. the titles are held by his grandson, the third Viscount, who succeeded his father in 1975.
The family previously owned Montgreenan Estate, near Torranyard, Ayrshire.
The heir apparent is the present holder's son, the Hon. James William Hartland Weir (b. 1965)
| Crest: | A Wing Argent charge with a Thistle slipped proper |
| Coronet: | A Coronet of a Viscount |
| Escutcheon: | Azure a Cogwheel Or winged Argent in chief the Sun in Splendour of the second |
| Supporters: | On either side a Winged Horse Argent hoofed and crined Or |
| Motto: | Forward Towards The Light |