San Buenaventura Mission Aqueduct, 18th century stone aqueduct in Ventura, California.

The San Buenaventura Mission Aqueduct was a seven-mile stone-and-mortar channel that carried water from the Ventura River to Mission San Buenaventura. The only significant surviving section, 100 feet long and ten feet high, stands at the mouth of Canyada canyon on Canada Larga Road, near the Ojai Freeway interchange.

Construction dates are disputed: one account places it between 1780 and 1790, when Chumash workers built it under a Spanish priest trained in hydrology; others put it in the 1790s, or between 1805 and 1815 under stonemasons brought from Mexico. The seven-mile stone and mortar channel carried Ventura River water to Mission San Buenaventura and its fields. The Great Flood of 1862 destroyed large sections, and settlers reused the stones for houses.

The aqueduct's construction is credited in one account to Chumash workers directed by a Spanish priest trained in hydrology; another credits stonemasons brought from Mexico between 1805 and 1815. The surviving section stands on land of Rancho Cañada Larga o Verde, held by the Canet family from 1873 into at least the 1960s.

The surviving section stands at 234 Canada Larga Road, near the interchange with the Ojai Freeway, on county-owned land at the mouth of Canyada canyon. It was fenced off in 1977 to deter vandalism, and the site has no guided tours; visitors view the 100-foot-long, ten-foot-high wall from outside the enclosure.

The surviving 100-foot section at Canyada Canyon is believed to have served as a siphon, drawing water uphill through conduits, according to the source. In 1989 a newly found three-foot piece was demolished during house construction; the owner then built his home over the aqueduct, keeping a 20-foot section in his basement.