The 1989–90 Lancashire Cup was the 77th occasion on which the Lancashire Cup competition had been held. Warrington won the trophy by beating Oldham by the score of 24-16 in the final. The match was played at Knowsley Road, Eccleston, St Helens, Merseyside, (historically in the county of Lancashire). The attendance was 9.990 and receipts were £41,804.

This season, Chorley Borough (see note 1) joined the league, bringing the total number of entrants up to 17.
This necessitated the need for a preliminary round (consisting of just 1 game). The first round (proper) then involved 16 clubs, thus removing the need of any "blank" or "dummy" fixtures or any byes.

1 * Chorley Borough (2) were elected to the league during the close season after the previous team of the same name moved out and to Altrincham as Trafford Borough. This was the first Lancashire Cup match played by the newly formed and elected club and also to be played at the new venue, home of Chorley F.C.
2 * The first Lancashire Cup match played by the reformed and newly named Trafford Borough The half time score was 2-6 in favour of Trafford Borough
3 * Match played at Leigh's Hilton Park
4 * Match played at Carlisle United's Brunton Park
5 * This was the 25th successive defeat for Runcorn Highfield
6 * The venue is given by RUGBYLEAGUEproject as Chiswick Poly Sports Grd - Rothmans Rugby League Yearbook 1990–91^[5] gives the venue as Claremont Road stadium which, at that date, was the home ground of Hendon F.C.
7 * The first Lancashire Cup match to be played on this ground, one of many used by Fulham during the nomadic period between 1985 and 1993
8 * Knowsley Road was the home ground of St. Helens from 1890 to 2010. The final capacity was in the region of 18,000, although the actual record attendance was 35,695, set on 26 December 1949, for a league game between St Helens and Wigan

• 1989–90 Rugby Football League season
• Rugby league county cups