Manyarara who died on Friday was an acting judge of the Namibian High Court where he was now based, media in that country reported.
He was the founding chairperson of the MISA Trust Fund Board and in 2001 the regional body launched an investigative journalism award in his honour.
He served on the board between 1994 and 2000.
Born on August 18, 1930 Manyarara obtained a law degree from the Rhodes University in South Africa before doing further studies in the UK.
He served on the High Court and Supreme Court benches in Zimbabwe before his retirement in 1994.
Manyarara then joined the Namibian High Court bench.
He was acting judge until his death.
In Namibia he presided over several high profile cases including the second part of the Caprivi treason trial, the largest in Nambian history.
But it was his battle for press freedom in the region that propelled him to prominence.