Dennis R. Washington (born 1934) is an American billionaire industrialist who owns, or co-owns controlling interests in, a large consortium of privately held companies collectively known as the Washington Companies and, in Canada, another collection of companies known as the Seaspan Marine Corporation.

Born in Spokane, Dennis Washington grew up in Spokane, Bremerton, Washington, and Missoula, Montana.^[1] His parents separated when he was very young, and Washington lived with his mother. He rarely saw his father, who worked in construction overseas. Washington did not grow up in a wealthy family. Additionally, he states his parents' divorce as his motivation to provide his own wife and children with a stable family environment.^[2]

Following graduation from high school, Dennis Washington worked in construction in Alaska and Montana. He began his business career at age 30 in 1964, with a $30,000 loan and a single bulldozer ^{[citation needed]}. He created Washington Construction, which worked primarily on highway contracts, and by 1969 was the largest contractor in Montana.^{[citation needed]}

In the 1970s he moved into mining and dam construction. In 1986 he acquired a copper and molybdenum mine at Butte, Montana. He reopened the mine and it became a profitable operation. This success helped him diversify into railroads, marine services, coastal shipping, aviation and real estate. In 1996 Washington Construction acquired global construction and engineering company Morrison-Knudsen Corporation^[3] of Boise, Idaho, creating Washington Group International.

The Washington Companies are a group of individual privately held companies headquartered throughout the United States and western Canada and conducting business internationally.

Included in the Washington Companies'^[4] holdings are:

• Seaspan ULC is an association of Canadian companies involved in coastal marine transportation, shipdocking and ship escort, ship repair and shipbuilding services in western North America.
• Montana Rail Link is a Class II regional railroad that operates over 900 route miles of track in Montana and Idaho.
• Aviation Partners Inc. develops and markets the Blended Winglet Performance Enhancement System for business jet aircraft. .
• Envirocon Inc.’s core services include environmental remediation, ecological restoration, and decommissioning and demolition for government and commercial clients.
• Southern Railway of British Columbia (SRY) is a major transporter of freight in British Columbia.
• Modern Machinery Co. Inc. sells and rents heavy equipment, and supplies parts and service to support the construction, mining, aggregate, and logging industries.
• Montana Resources LLP operates an open-pit copper and molybdenum mine in Butte, Montana, near the Continental Divide.
• Seaspan Corporation (NYSE:SSW) is one of the world’s leading independent containership owners, owning and managing ships which are chartered long-term.

Together with his spouse, Washington contributed $1 million to Donald Trump's 2020 presidential campaign.^[5]

Washington is married to Phyllis and lives in Missoula, Montana. His son, Kyle Washington, is co-chairman of Seaspan Marine Corporation.^[6]

Washington also owns a private estate on Stuart Island, British Columbia, including a fishing lodge and golf course. The Washington–Grizzly Stadium for football at the University of Montana is named for him.^[7]

His private yacht Attessa IV has been featured in Forbes magazine.^[8] He has a Boeing Business Jet, 737-700 registration N162WC.^[9]

• List of billionaires