United will launch three-times per week service from Washington Dulles to Lagos, Nigeria, on Nov. 29.
The flight will be the only direct connection between the U.S. capital and sub-Saharan Africa's largest city.
Africa aviation news:
Africa Insight: United's new nonstop flight lifts spirits
Delta and Kenya Airways expand codesharing
South African Airways emerges from yearlong hiatus
United will operate the service with a Boeing 787 Dreamliner configured with a business cabin, a premium economy cabin and an economy cabin.
The new route will be United's second to West Africa from D.C., joining the Accra, Ghana, flights the carrier began in May.
Dulles also serves as a gateway for three other African cities: Casablanca, Morocco, on Royal Air Maroc; Addis Ababa, Ethiopia, on Ethiopian Airlines; and Cairo on Egypt Air, Cirium flight schedule data shows.
Delta operates the two U.S. routes to Lagos, flying from New York JFK and Atlanta.