The following lists events that happened during 1990 in the Democratic Republic of São Tomé and Príncipe.
Incumbents President: Leonel Mário d'Alva (acting) Prime Minister: Celestino Rocha da Costa
Events May: politician Miguel Trovoada returned to São Tomé and Príncipe from exile in France 22 August: A Constitutional referendum took place, it became a multi-party democracy October: at the MLSTP party Congress, Carlos Graça was appointed as the new Secretary-General of the party. In addition, the party's name was amended to the Movement for the Liberation of São Tomé and Príncipe/Social Democratic Party (MLSTP/PSD). 4 November: the Democratic Convergence Party – Reflection Group (PCD-CR) was founded
Sports GD Os Operários won the São Tomé and Príncipe Football Championship
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