Cenovus Energy says it will pay $13.2 billion for most of ConocoPhillips' Canadian assets.
Houston-based ConocoPhillips is the latest company to reduce exposure to Canada's oil sands — the world's third-largest oil reserves.
Cenovus CEO Brian Ferguson called it a "transformational acquisition" for the Calgary-based company.
Royal Dutch Shell earlier this month sold most of its oil sands holdings to Canadian Natural Resources Ltd.
Oil sands are a type of unconventional petroleum deposit.