The cause of death was not disclosed, but the Raiders Web site said Davis' family would make an announcement later in the day.
The Raiders were in Houston preparing for Sunday's game against the Texans. NFL.com said the players were informed of Davis' passing during a morning meeting, which was then quickly adjourned.
"He is a legend and an icon and we're going to honor him by playing the way the Raiders should play," said coach Hue Jackson, who referred to Davis as "coach." NFL.com said several players appeared choked up after hearing the news.
Davis had an open-door policy with his players. Although he was known to be slowing down, his death appeared to be a shock.
The future leadership of the Raiders front office was not immediately discussed.
Davis was a legendary pioneer of professional football in the United States. He joined the Raiders as head coach and general manager in 1963 and rose to become the majority owner of the team.
He was considered a leader of the upstart American Football League's challenge to the National Football League and its eventual merger with the NFL, NBC Sports said. He entered the Pro Football Hall of Fame in 1992.
The Raiders won three Super Bowls under Davis and also moved from Oakland to Los Angeles and back to Oakland.
NFL Commissioner Roger Goodell issued a statement calling Davis a "true legend of the game."
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