She was buried alongside her husband King George VI.
The ashes of her daughter Princess Margaret who died eight weeks ago were also placed in the black marble-covered vault.
The Queen Mother's coffin had earlier travelled in a hearse from Westminster Abbey accompanied by her grandson Prince Charles.
A million people lined the final route and stood silently as it passed on its way from the abbey towards Windsor.
Others clapped or threw flowers.
As the hearse travelled along the Mall, two World War II Spitfire planes and a Lancaster bomber flew overhead.
These were a tribute to the Queen Mother's refusal to leave London when it was being bombed during the war.