The Vatican announced on Wednesday that Francis had approved a decree the previous day during a meeting with the head of the Vatican's saint-making office.
Also approved was the miracle attributed to Pope Paul VI, paving the way for his canonisation.
Mr Romero was gunned down by right-wing death squads on March 24 1980, as he celebrated mass. El Salvador's military dictatorship had vehemently opposed his preaching against the repression of the poor by the army at the start of the country's 1980-1992 civil war.
Francis unblocked Mr Romero's long-stalled sainthood case at the start of his pontificate and declared him a martyr in 2015.
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