Twenty Mile Bay is a provincial recreation site and campground on the west shore of Harrison Lake in the Fraser Valley of British Columbia, roughly 1. 5 hours northeast of Mission.

It is reached via approximately 38 kilometres of the Sts'ailes Forest Service Road — a gravel route that is passable by most vehicles but expect a bumpy, dusty drive.

The campground occupies a forested peninsula set within old-growth conifers, with about 52 campsites spread along 1. 5 kilometres of rocky beach offering both north- and south-facing lake views.

North-facing sites look out toward snow-capped Mount Breakenridge. More than half the sites sit directly on the waterfront. The site has no electricity, potable water, or garbage disposal; visitors must bring their own water and pack out all waste.

Outhouses are available on site.