According to the United States Census Bureau, the city has an area of 6.1 square miles (15.8 km²), over 99% of it land.
To the north of Hawthorne is the unincorporated community of Lennox and the city of Inglewood. To the east is the unincorporated community of Athens and the city of Gardena. To the south is the unincorporated community of El Camino Village, and the cities of Lawndale and Redondo Beach. Manhattan Beach is at the southwest corner of Hawthorne, and the city of El Segundo is to the west of Hawthorne. The unincorporated community of Del Aire is surrounded on three sides by the city of Hawthorne along western edge of Hawthorne.