Wesker is a former captain of S.T.A.R.S. He is the developer of the T-Virus and a specialist in germ warfare. He secretly spread around the virus.

Power-hungry, intelligent and cunning, Albert Wesker was a man who sought power and domination over the entire human race, all for his own gain. To this end, he was affiliated with the Umbrella Corporation, as one of its most promising researchers, and at the same time participated in illicit activities by going undercover as an officer in the R.P.D. He founded the S.T.A.R.S. unit and became its lead captain. This changed before, during, and after the Raccoon City Outbreak, where Wesker became affiliated with a mysterious group known as the "Organization", and became instrumental in bringing about the downfall of Umbrella. Wesker planned to remake Umbrella as his own empire, and contacted numerous other Umbrella rivals to gain profit to achieve this.

Afterwards, he joined Tricell, Inc. to recreate the entire world in his own image. His ultimate goal was to lead the human race into a new era under his leadership, as he thought the world was in a state that would inevitably bring about its own destruction. Through the course of his campaign, Wesker fought a seemingly never ending battle with Chris Redfield and Jill Valentine, former S.T.A.R.S. agents and the most persistent of his enemies. He came to deeply hate the two as the years went on, growing an immense desire for revenge.

Initially the main villain of the original Resident Evil, since his reappearance in CODE: Veronica, manipulation of the story events from behind-the-scenes in further games, and role as main villain in Resident Evil 5, Wesker is considered by many fans and official sources to be the primary antagonist of the entire Resident Evil series, even surpassing Ozwell E. Spencer. He was also portrayed as the primary antagonist of the Resident Evil films, where he again operated from behind-the-scenes.