Patrick Gass, American sergeant (Lewis and Clark Expedition) and author (died 1870)

Patrick Gass served as sergeant in the Lewis and Clark Expedition (1804–1806). He was important to the expedition because of his service as a carpenter, and he published the first journal of the expedition in 1807, seven years before the first publication based on Lewis and Clark's journals.

The Lewis and Clark Expedition, also known as the Corps of Discovery Expedition, was the United States expedition to cross the newly acquired western portion of the country after the Louisiana Purchase. The Corps of Discovery was a select group of U.S. Army and civilian volunteers under the command of Captain Meriwether Lewis and his close friend Second Lieutenant William Clark. Clark, along with 30 others, set out from Camp Dubois, Illinois, on May 14, 1804, met Lewis and ten other members of the group in St. Charles, Missouri, then went up the Missouri River. The expedition crossed the Continental Divide of the Americas near the Lemhi Pass, eventually coming to the Columbia River, and the Pacific Ocean in 1805. The return voyage began on March 23, 1806, at Fort Clatsop, Oregon, ending six months later on September 23 of that year.