| Intro | São Tomé and Príncipe politician |
| Is |
Politician Diplomat |
| From | Sao Tomé and Príncipe |
| Type | Politics |
| Gender | male |
| Birth |
18 May 1953, São Tomé Island, São Tomé and Príncipe |
| Age | 67 years |
| Star sign | Taurus |
| Politics | Movement for the Liberation of São Tomé and Príncipe/Social Democratic Party |
Guilherme Posser da Costa (born 1953) was Prime Minister of São Tomé and Príncipe from 1999 to 2001.
Posser da Costa served as Minister of Foreign Affairs on three different occasions: 1987-1988, 1990-1991, and 1994-1996. He later served as Prime Minister from 5 January 1999 to 26 September 2001.
In early November 2004, Posser da Costa allegedly damaged the office of Attorney General Adelino Pereira in an attack. Pereira said this was due to an investigation regarding embezzlement of aid funds and ordered Posser da Costa’s arrest. Due to the alleged attack, Posser da Costa resigned from parliament on 15 February 2005, just before his parliamentary immunity was to be removed. On 18 March 2005, he received a two-year suspended sentence for damaging Pereira’s office and “insulting public authority”; he was also required to pay compensation. For his part, Posser da Costa said that Pereira had falsely accused him of being involved in the embezzlement of aid funds, and that he had only been a witness in that case, not a suspect.
At the Fourth Congress of the Movement for the Liberation of São Tomé and Príncipe/Social Democratic Party (MLSTP/PSD), Posser da Costa was elected as President of the MLSTP/PSD on 27 February 2005, succeeding party founder and former President Manuel Pinto da Costa. There were 708 votes in favor of Posser da Costa, who was the only candidate, and three votes against him.