Petronius is a deepwater compliant tower oil platform operated by Chevron Corporation and Marathon Oil in the Gulf of Mexico, 210 km southeast of New Orleans.

A compliant piled tower design, it is 609.9 meters (2,001 feet) high, arguably the tallest free-standing structure in the world, although this claim is controversial since only 75 meters of the platform are above water. The multi-deck topsides are 64 meters by 43 meters by 18.3 meters high and hold 21 well slots, and the entire structure weighs around 43,000 tons. Around 8,000 m³ (50,000 barrels) of oil and 2,000,000 m³ (70 million cubic feet) of natural gas are extracted daily by the rig.

The platform is situated to exploit the Petronius field, discovered in 1995 in Viosca Knoll and named after Petronius, the Roman writer. The seabed is 535 m (1,754 feet) below the platform. The compliant tower design is more flexible than conventional land structures to cope better with sea forces. It can deflect (sway) in excess of 2% of height. Most buildings are kept to within 0.5% of height in order to have occupants not feel uneasy during periods of movement.

Construction began in 1997 by J Ray McDermott with the seabed mooring system. The contract for the platform was budgeted at $200 million with total costs of around $500 million. The 4,000-ton North Module was installed in November 1998, but the attempt to install the slightly lighter South Module in December of that year ended with the unit on the seabed. A replacement module was built and installed by Saipem 7000 in May 2000.