The A5091 is a short A-road in the eastern Lake District. The road was originally numbered B5288 before being upgraded to receive its current number in the mid-1920s.
Starting on the pretty shores of Ullswater a couple of miles north of Glenridding and Patterdale at the lakes southern end, the A5091 immediately starts climbing northwards past the waterfall of Aira Force and into the little village of Dockray. Here the road turns sharp right over an old stone bridge, in front of the hotel. Still climbing, the road heads on towards Matterdale End, passing the church on the right and so through the village. After crossing the summit in the forestry, the road picks up the valley of the Trout Beck, and becomes noticeably wider as it sweeps down hill in a series of fast curves, reaching the A66 (former A594) a couple of miles west of Penruddock.