No cause of death was given. The former queen consort had suffered from osteoporosis for years, however, and had never fully recovered from a lung inflammation she had in 2009.
"Their majesties the king and queen and the members of the royal family announce with very great sadness the death of Her Majesty Queen Fabiola this evening at Stuyvenberg Castle in Brussels," a statement from the royal palace of King Philippe said.
The royal, who used a wheelchair had limited her public appearances as of late, and had appeared increasingly frail.
Fabiola became queen of Belgium on the occasion of her marriage – she wed King Baudouin in 1960. She was queen for 33 years, until her husband died in 1993.
As the couple had no children, the throne passed to King Baudouin's younger brother, who became King Albert II. He abdicated last July, passing the baton to his son, King Philippe.
Queen Fabiola was born Fabiola de Mora y Aragón in 1928 into an aristocratic family in the Spanish capital of Madrid.
During her time in the royal spotlight she was involved in humanitarian causes, particularly children's issues and the rights of women in developing countries.