Santos, who will be 60 next month, is a former coach of Greece, whom he took to the quarter-finals of the 2012 European Championship and the round of 16 in the World Cup in Brazil.
Santos quit Greece after the World Cup, his post taken up by Claudio Ranieri.
His final game in charge was tinged with sadness as he was sent from the touchline by Australian referee Ben Williams prior to the penalty shoot-out that saw his Greece side beaten 5-3 by Costa Rica, who went on to a quarter-final meeting with the Netherlands.
Santos got into an exchange with the official and was forced to watch the penalty shoot-out from an office in the belly of the Arena Pernambuco in Recife.
The Portuguese also has a wealth of club coaching behind him, having managed Estoril, Estrela da Amadora, Porto, Sporting and Benfica in Portugal and AEK Athens (twice), Panathinaikos and PAOK in Greece.
His first aim will be to help Portugal qualify for the 2016 European Championship in France, the side having suffered a shock 1-0 opening qualifying loss at home to Albania - a result which saw Bento quit by mutual consent.
Next up for Portugal are away matches against France on October 11 in a friendly, and Denmark three days later.
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