Pharmacia was originally a government owned Swedish pharmaceutical company. Sold to private interests in the 1990s, it was first merged with the American pharmaceutical company Upjohn and headquartered in London. The merged company Pharmacia & Upjohn was there after bought by the American bioindustry and medical company Monsanto. The resulting conglomerate took the name of Pharmacia Inc and spun off its agricultural chemical division under the name Monsanto.

In 2002 Pharmacia was bought by Pfizer Inc, and the name Pharmacia was dropped.