Agua Mansa (Spanish for "gentle water")[2] is a former settlement in an unincorporated area of San Bernardino County, near Colton, California, United States.

[10] In 1845, Don Juan Bandini donated parts of his land grant Rancho Jurupa to a group of New Mexican colonists led by Santiago Martinez, and Manuel Lorenzo Trujillo from Abiquiú in Santa Fe de Nuevo México — on the condition that they would provide in protection from local Indian raids, in exchange for land, "Civil Militia" Ten of these families moved to 2,000 acres (810 ha) on the "Bandini Donation" on the east side of the Santa Ana River, forming the village of La Placita, while a second group colonized the west side of the river, forming the town of Agua Mansa.

[12] The town prospered for almost 20 years until the 1862 flooding swept away many of the adobe buildings, leaving the area strewn with sand and gravel.

[14] The marker is located at Agua Mansa Pioneer Cemetery, the only site that remains of the once flourishing town.

The earliest known interment was that of Louis Rubidoux, who came to California in 1844 and bought the Jurupa Rancho near today's City of Riverside.

Lorenzo Trujillo, the original patriarch of the community, is also believed to rest somewhere in a grave that long ago lost its marker.

[8][16] Agua Mansa is the namesake of a fictional town in Southern California in the contemporary novel Still Water Saints by writer Alex Espinoza.