Weyerhaeuser (pronounced "Warehouser") is one of the world's largest private owners of timberlands. It owns more than 13 million acres of timberlands, primarily in the U.S., and manages another 14 million acres under long-term licenses in Canada. The company also manufactures wood and cellulose fiber products. Weyerhaeuser is a real estate investment trust.

In 1900, after years of successful Mississippi River-based lumber and mill operations with Frederick Denkmann and others, Frederick Weyerhaeuser moved west to fresh timber areas and founded the Weyerhaeuser Timber Company. Fifteen partners and 900,000 acres (3,600 km²) of Washington timberland were involved in the founding, and the land was purchased from James J. Hill of the Great Northern Railway. In 1929, the company built what was then the world's largest sawmill in Longview, Washington. Weyerhaeuser's pulp mill in Longview, which began production in 1931, sustained the company financially during the Great Depression. In 1959, the company eliminated the word "Timber" from its name to better reflect its operations. In 1965, Weyerhaeuser built its first bleached kraft pulp mill in Canada. Weyerhaeuser implemented its High Yield Forestry Plan in 1967 which drew upon 30 years of forestry research and field experience. It called for the planting of seedlings within one year of a harvest, soil fertilization, thinning, rehabilitation of brushlands, and, eventually, genetic improvement of trees.

Weyerhaeuser consolidated its core businesses in the late 1990s and ended its services in mortgage banking, personal care products, financial services, and information systems consulting. Weyerhaeuser also expanded into South America, Australia, and Asia. In 1999, Weyerhaeuser purchased MacMillan Bloedel Limited, a large Canadian forestry company. Then in 2002 after a protracted hostile buyout, the company acquired Willamette Industries, Inc. of Portland, Oregon. On August 23, 2006, Weyerhaeuser announced a deal which spun off its fine paper business to be combined with Domtar, a $3.3 billion cash and stock deal leaving Weyerhaeuser stock holders with 55 percent ownership of the new Domtar company.

In March 2008, Weyerhaeuser Company announced the sale of its Containerboard Packaging and Recycling business to International Paper for $6 billion in cash, subject to post closing adjustments. The transaction included nine containerboard mills, 72 packaging locations, 10 specialty-packaging plants, four kraft bag and sack locations and 19 recycling facilities. The transaction affected approximately 14,300 employees.

Weyerhaeuser converted into a real estate investment trust when it filed its 2010 tax return.

In 2013, Weyerhaeuser purchased Longview Timber for $2.65 billion including debt from Brookfield Asset Management. The acquisition added 645,000 acres of timberland to Weyerhaeuser's holdings in Oregon and Washington.

In 2014, Weyerhaeuser spun off its home building unit to TRI Pointe Homes in a $2.8 billion transaction. The company also announced its intention to sell its Federal Way headquarters and relocate to Seattle's Pioneer Square in 2016. The sale and move were completed in 2016.

On November 8, 2015, it was announced that Weyerhaeuser would buy Plum Creek Timber for $8.4 billion, forming the largest private owner of timberland in the United States. The transaction closed on February 19th, 2016.

The company's operations are divided into three major business segments:

Doyle Simons is the CEO and president of Weyerhaeuser Company. The Weyerhaeuser board of directors consists of: Debra A. Cafaro, Mark Emmert, John I. Kieckhefer, Wayne W. Murdy, Nicole Piasecki, Doyle R. Simons, Richard Sinkfield, D. Michael Steuert, Kim Williams and Charles Williamson.