The 1945–46 Lancashire Cup was the thirty-third occasion on which the Lancashire Cup competition had been held in rugby league, and the first since the end of the Second World War in Europe.
For the first time for several seasons there is a new name on the trophy; that of one of the founder members of the Northern Union, Widnes, who won the trophy by beating Wigan by the score of 7–3.
The match was played at Wilderspool, Warrington, (historically in the county of Lancashire). The attendance was 28,184 and receipts were £2,600.

The number of teams entering showed little change from before the war.
St Helens Recs had already withdrawn from the league immediately after the end on the 1938–39 season. The club had been struggling to survive for a few years with falling attendances and the economic depression and it was obviously not possible for the town to sustain two top teams.
Leigh lost its ground to in August 1940 when Callender's Cable and Construction Company bought the Mather Lane site to store drums etc as part of the war effort. The club did not resume playing until the 1946–47 season when they found a temporary ground.
Workington Town from Cumberland had joined the league.
Overall, the number of teams entering this year's competition had decreased from the pre-war total by just one and was now 12. The same pre-war fixture format was retained. This season saw no byes but two "blank" or "dummy" fixture in the first round. The second round now had two byes.
The first round of the competition was played on the basis of two legged, home and away, ties.

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• 1945–46 Northern Rugby Football League season
• Rugby league county cups