Legendary offensive tackle Bob Brown died at 81 on Friday night in Oakland, California, the Pro Football Hall of Fame announced Saturday.

Brown’s wife, Cecelia, said he died surrounded by friends and family at a rehabilitation center, where he had been admitted following a stroke in April.

The six-time Pro Bowler and five-time All-Pro — who was nicknamed “the Boomer” — was described as a “fierce” competitor by the Pro Football Hall of Fame.

“Bob Brown demonstrated different personalities on and off the field,” Pro Football Hall of Fame president Jim Porter said in a statement. “On the field, he was as fierce an opponent as any defensive linemen or linebacker ever faced. He used every tactic and technique — and sometimes brute force — to crush the will of the person across the line from him. And took great pride in doing so.

“Yet off the field, he demonstrated a quiet, soft-spoken and caring nature that his son, Robert Jr., captured eloquently when he presented his dad for enshrinement in 2004. The Hall extends its thoughts and prayers to CeeCee and Robert Jr. for their loss.”

Brown started his career as a guard at the University of Nebraska, where he became an All-American.

After his successful college career — that eventually landed him in the College Football Hall of Fame in 1993 — the Eagles drafted Brown as the No. 2 overall pick in the 1964 draft.

He also was taken in the American Football League’s draft by the Broncos that year but decided to join the NFL’s Eagles, with whom he played five seasons.

He then spent two seasons with the Rams before going to the Raiders for the final three years of his career.

Brown’s legendary playing career earned him a spot on the NFL’s 1960s All-Decade Team, and he was later inducted into the Pro Football Hall of Fame in 2004.

The Hall of Fame will fly the flag at half-staff in remembrance of Brown.