The 1990–91 Pilkington Cup was the 20th edition of England's, premier (at that time) rugby union club competition.

Harlequins won the competition, for the second time, defeating Northampton 25 – 13 at Twickenham.

[1] The event was sponsored by Pilkington.

[2][3]

The competition was sponsored by Pilkington who had provided £700,000 over the first three seasons and agreed to a further three years worth £1,000,000.