Nii Okaidja Adamafio is a former Ghanaian politician. He was the Minister of the Interior in the Rawlings government from 1997 to 2001. He was a Member of Parliament from 1992 to 1997 in the Odododiodoo constituency.
As a member of the National Democratic Congress (NDC), Adamafio rose to be vice-chairman of the party. In the 1996 elections he was returned as MP for Odododiodoo with 29,142 votes (35.4%). In the 2000 election he secured 24,181 votes (43.9%), losing his seat to Reginald Niibi Ayibonte.
In February 2006 he resigned from the NDC. In 2008 he became the vice-chairman of the Democratic Freedom Party (DFP).