Masire had been heavily involved in efforts to end violence between Mozambique's government and the main opposition.
Masire had been heavily involved in efforts to end violence between Mozambique's government and the main opposition Renamo party in his role as co-chair of an international group of mediators.
Renamo, which waged a 16-year civil war that ended in 1992, refused to accept the results of 2014 elections when it was beaten once more by the Frelimo party, sparking clashes across the country last year.
Masire passed away in a hospital in Botswana's capital Gaborone late on Thursday, according to his senior private secretary Fraser Tlhoiwe.
"He died peacefully at Bokamoso private hospital surrounded by his family at 10:10 pm on 22 June 2017. We thank well-wishers and friends from near and far, for their prayers, thoughts and comforting messages of support during this difficult time," Tlhoiwe said in a statement.
Masire was hospitalised for surgery on June 16 according to his family and despite being admitted to intensive care was thought to be in a stable condition.
Masire led Botswana following president Seretse Khama's death in 1980 until voluntarily stepping down 1998, having overseen a period of unprecedented economic growth. He is largely credited with being the architect of Botswana's famed stability.
As well as mediating to end violence in Mozambique, Masire also helped to resolve political crises in Kenya and Lesotho after leaving office, in his role as one of Africa's most respected elder statesman.
He was also the chair of the International Panel of Eminent Personalities investigating the circumstances of the 1994 Rwanda genocide.
One of Africa's most stable countries, Botswana is a republic in which Masire's Bechuanaland Democratic Party (BDP) -- now known as the Botswana Democratic Party -- has been in power since independence.
Botswana has enjoyed uninterrupted civilian rule since independence in 1966.