Swiftsure was a 42-gun great ship of the English Royal Navy, built by Andrew Burrell at Deptford and launched in 1621.

[2] In May 1660, during the English restoration, she seems to have carried Henry Stuart, Duke of Gloucester from Scheveningen to Dover.

[3] She was the flagship of Vice-Admiral Sir William Berkeley at the Four Days' Battle against the Dutch in 1666.

[4] Berkeley led the van of the English fleet on the first day of the battle, 1 June, but outsailed his squadron into the midst of the Dutch, and was surrounded.

[2][4] The Dutch renamed her the Oudshoorn (70 cannon) and changed the quartergalleries to hide her identity.