Pope Francis will canonise Joseph Vaz at a public mass on the Colombo seafront tomorrow which is expected to be attended by a million devotees.
The pope is expected to preach a message of reconciliation during his visit to Sri Lanka, which only recently emerged from a long civil war between government troops and Tamil separatists.
Although Sri Lanka has claimed him as its first saint, Vaz was actually born in Goa on India's west coast -- then a Portuguese colony.
Vaz travelled from village to village ministering to Catholics from both the Tamil and the majority Sinhalese ethnic groups.
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He had to disguise himself as a beggar because the Dutch had banned Catholic priests from the island, and he spent several of his 23 years in Sri Lanka in jail for his work.
By the time of his death in 1711 he had largely rebuilt the Catholic Church, earning him the title "Apostle of Sri Lanka".
"The people who saw him work were amazed," said Sri Lankan priest Anthony Fernandopulle.
"What he did so bravely, even at the risk of contracting the disease himself, was in their eyes a miracle of charity."
Vaz was beatified by Pope John Paul II during a brief one-day visit to Sri Lanka in 1995.
He is credited with one miracle -- the survival of a baby boy whose mother prayed to him after she was told her child had only a one percent chance of living.