HMCS Thunder (pennant J156) was a Bangor-class minesweeper constructed for the Royal Canadian Navy during the Second World War.

The engines produced a total of 2,400 indicated horsepower (1,800 kW) and gave a maximum speed of 16.5 knots (30.6 km/h; 19.0 mph).

[6] Thunder had her 2-pounder gun replaced with a powered twin 20 mm mount in preparation for duties associated with the invasion of Normandy.

[2][5] The minesweeper was ordered as part of the 1939–40 building programme[6] and the keel was laid down on 4 December 1940 by Dufferin Shipbuilding Co. at their yard in Toronto, Ontario.

[7] The minesweeper sailed to Europe via the Azores in February 1944 as part of the Canadian contribution to the invasion of Normandy.

[12] This took the flotilla ten days to complete, after which Thunder was ordered to join American minesweepers for the assault on Cherbourg.

[13] On 24 June, during the preliminary bombardment, the minesweeping force of which Thunder was a member, arrived off Point Barfleur in mid-afternoon.

Sailing to the Gironde estuary on 12 April, the minesweeping flotilla swept an invasion channel for the attack force landing in the area.

While transiting the Bay of Biscay, Thunder accepted the surrender of the German auxiliary minesweeper FGi 07 and with a prize crew aboard, took the vessel back to the United Kingdom.