Big Rock is a primitive, free fishing access campground with approximately 5-6 sites located directly on the Boulder River near Big Timber, Montana, offering excellent river access for fishing and swimming.

The site features pit toilets, fire rings, and some picnic tables, with several sites positioned right on the riverbank; however, there is no drinking water, hookups, or trash service (pack-in/pack-out required).

Access is via a well-maintained gravel road about 10 minutes from Interstate 90, though the road can be rough and washboard-like, and a Montana Conservation License is required to camp here.