SS Sansinena was a Liberian oil tanker that exploded in Los Angeles harbor on 17 December 1976 at 7:33pm. She was docked at berth 46 at Port of Los Angeles in San Pedro, California.

The vessel was a steamship built in 1958. At its final port of call, Sansinena had discharged its cargo of crude oil and was taking on ballast and fuel when a massive explosion split the ship in half and obliterated multiple port buildings. The blast shattered windows for miles around, flung the entire midship bridge on the wharf, and triggered a fire that spread across the dock and around the tanker. The Los Angeles Fire Department soon arrived on the scene to contain the blaze and rescue survivors. One of the fires, fed by underground fuel lines, burned for four days.

A United States Coast Guard investigation later concluded that the incident was caused by flammable hydrocarbon vapor buildup on the deck of the ship caused by a poorly designed and deteriorating venting system as well as an unsafe practice (leaving all vents open during ballasting). The ignition source was never identified.

The official casualty count was:

• 9 dead (eight crew and one dock security guard).
• 46 injured, 9 requiring hospitalization.

The explosion of Sansinena and technical details of the incident were featured as the first segment of the Engineering Disasters in an episode of History Channel's Modern Marvels television series.

The winter of 1976–77 was a particularly bad period of oil spills and ship accidents in the US. MV Argo Merchant, SS Grand Zenith, MV Hawaiian Patriot and other ships had incidents at this time. The United States' National Oceanic and Atmospheric Administration began a spill response program in response to these events.

• Ralph J. Scott (fireboat)

• Eppink, John J (March 1977). "M/T Sansinena Explosion". The Navigator. p. 47.

• Jerricks, Terelle (ed.). "The Blast Zone Remembering the S.S. Sansinena 29 Years Later". Random Lengths News. Archived from the original on 2012-06-23.
• "Marine Casualty Report SS Sansinena (Liberian) Explosion and Fire in Los Angeles Harbor on 17 December 1976 with Loss of Life" (PDF). National Chemical Safety Program. United States Coast Guard. 25 November 1977. USCG 16732/71895.
• "SS Sansinena (Liberian); Explosion and Fire in Los Angeles Harbor, California on 17 December 1976 with Loss of Life". Defense Technical Information Center (Abstract). ADA049805. Archived from the original on July 22, 2011.
• "Sansinena Los Angeles Harbor, California 1976-Dec-17". Incident News. Archived from the original on 2012-03-14.
• "Sansinena". California Fireman. Los Angeles Fire Department Historical Society. February 1977. Archived from the original on 2016-04-17.
• "LAFD- the S.S. Sansinena Tank Ship Explosion, Marine Casualty Report-U.S. Coast Guard". Los Angeles Fire Department Historical Society. Archived from the original on 2020-02-22.
• "Berth 46 - S.S. Sansinena Explosion Site (Los Angeles, California)". Wikimapia.

33°42′52″N 118°16′29″W / 33.71444°N 118.27472°W / 33.71444; -118.27472