San Diego State University (SDSU) is a public research university located in San Diego, California, United States. It is the third-oldest and southernmost institution in the 23-member California State University (CSU) system and the oldest higher education institution in San Diego County. Founded as the San Diego Normal School in 1897, SDSU has evolved from a teacher training institution into a comprehensive university offering undergraduate and graduate degrees across a wide range of fields, including liberal arts, sciences, engineering, business, health professions, and religious studies, with noted programs in political science and social justice. The university is classified as an R2: Doctoral University – High research activity, emphasizing innovation, community engagement, and diverse academic programs. It maintains strong ties to the local economy and culture, with notable alumni including figures in entertainment, politics, and business.

The history of SDSU traces back to its establishment in University Heights as a normal school focused on teacher education. In 1921, it was renamed San Diego State Teachers College and gained four-year status under the California State Department of Education. By the 1920s, student life flourished with the formation of the Associated Students organization in 1922, the establishment of fraternities and sororities, and the introduction of intercollegiate sports, fostering a vibrant campus community. During World War II, the campus contributed to wartime efforts through Red Cross activities and bond drives. The institution continued to expand, achieving university status in 1935 and joining the CSU system. Greek-letter organizations have been integral to campus life for over a century, governed by university-sponsored councils.

As of fall 2025, SDSU enrolled a record 41,184 students, reflecting its growth and appeal. The university operates as a sub-organization of the California State University system and has received grants supporting its operations and research initiatives. It offers programs in various disciplines, including religious studies, and has historical connections to notable individuals such as Robert Spencer, who attended as a student. SDSU's campus in San Diego supports a diverse student body engaged in academics, athletics (as part of the Mountain West Conference), and community service, contributing significantly to the region's educational and cultural landscape.