| Usulután | |
| Settlement Type: | Department |
| Mapsize: | frameless |
| Coordinates: | 13.376°N -88.52°W |
| Subdivision Type: | Country |
| Subdivision Name: |  El Salvador |
| Established Title: | Created |
| Established Date: | 1865 |
| Seat: | Usulután |
| Area Total Km2: | 2130.4 |
| Area Rank: | Ranked 1st |
| Population Total: | 366040 |
| Population Density Km2: | auto |
| Population Rank: | Ranked 5th |
| Timezone: | CST |
| Utc Offset: | −6 |
| Area Code Type: | Calling code |
| Iso Code: | SV-US |
Usulután (pronounced as /es/; from the Nawat language, meaning "city of the ocelots") is a department of El Salvador in the southeast of the country (Lenca region). The capital is Usulután.
Created on June 22, 1865, it is El Salvador's largest department. It has an area of 2,130 km² and a population of over 366,000.
On October 26, 1948, the Alegria district was abolished and a new one called Santiago de Maria was created; it contains the cities of Santiago de Maria, which is the main city, as well as Alegria, Tecapan and California.
The city of Usulutan, the department's capital, was founded by the Lenca tribes but it was conquered by the Pipil tribes. Some of the best beaches in El Salvador are located in Usulutan, and others such as El Espino are now under development. For its high migration of its residents to the United States, it is known as Shulton city.
The department is home to Jiquilisco Bay and Port El Triunfo.
Bosque Nancuchiname is a forest of the Usulután Department, framing the eastern bank of the Lempa River and the town of El Zamoran on its southeastern border.