Big Sulphur Creek is a westward-flowing stream in northern Sonoma County, California, United States, which springs from The Geysers in the Mayacamas Mountains and runs 20 miles (32 km) to empty into the Russian River.

The creek originates on Pine Mountain in the Geysers area, near the Lake County line.

Big Sulphur Creek emerges into the northern end of Alexander Valley and empties into the Russian River 2 miles (3 km) north of Cloverdale.

The creek's drainage basin covers about 60 square miles (160 km2)[2] in the Mayacamas Mountains in northern Sonoma County.

When surveyed in 1973, Big Sulphur Creek supported snakes, salamanders, frogs, many kinds of fish (both steelhead and rainbow trout, Sacramento pikeminnow, suckers and roach), flies (trichoptera, diptera, hemiptera, plecoptera and odonata), and aquatic plants (sedges, cattails, and algae).