Portugal, in the 12th century, began as a county, that is, governed by a count. According to Mel Nicholls  the Bell Beaker culture originated in Portugal around 2800 BC. Nicholls has nominated the Beaker people in Britain as Atlantean, whereas Donald Ingram argues that their successors in Britain, the Wessex II culture was Atlantean.
Portugal entered the Atlantis Stakes with a claim by a Basque researcher, Luis Aldamiz, that a little-known ancient civilisation, known as the Villa Nova de São Pedro (VNSP) culture matched much of Plato’s description of Atlantis(b). Its capital was Zambujal, which was located on a mountain in the centre of the Estramadura peninsula, near modern Lisbon. Originally it was described as a ‘perriruthos’, which indicates something surrounded by water. Aldamiz notes that ten tombs were found there; reminiscent of the ten kings of Atlantis. Zambujal had large complex fortifications. Aldamiz claims that this civilisation fought against the Greeks during the Middle Bronze Age. He further believes that the destruction of his Atlantis was caused by an event that was similar to the 1755 Lisbon earthquake that caused such death and destruction.
Lereno Barradas was a Portuguese writer who speculated in the early 1970s that Tartessos could be identified with Atlantis and that it had been located in the Tagus estuary near the site of modern Lisbon. He also suggested that these ancient Atlanteans had travelled to America.
In 1989 another Portuguese researcher, José Antunes, proposed that Atlantis had been situated in what is now northwest of Lisbon between Sintra and Mafra.
A more radical theory has been put forward by Roger Coghill, the British bioelectromagnetic investigator, who suggests on his website that Atlantis was located in the vicinity of Faro in the Algarve. Coghill expanded on his theory in his book, The Message of Atlantis. He has also drawn attention to a book  by Antonio Jose Lopes Navarro, published in 1983, in which he has brought together a number of classical references to the prehistory of the Algarve.
Portugal got further attention in 2013 when another British researcher, Peter Daughtrey, who then lived in Portugal, published Atlantis and the Silver City  in which he designates not just the Algarve and the submerged area in front of it as Atlantis, but the whole of that south-west Iberian region.
Manuel J.Gandra has produced a valuable bibliography(c) of Portuguese sources dealing with Atlantis.