The 186th Aero Squadron was a Air Service, United States Army unit that fought on the Western Front during World War I. The squadron was assigned as an Army Observation Squadron, performing long-range, strategic reconnaissance over the entire length of the United States First Army sector of the Western Front in France. After the 1918 Armistice with Germany, the squadron was assigned to the United States Third Army, VII Corps Observation Group at Trier Airfield, Germany as part of the Allied Occupation of the Rhineland.