Catholics World News and Catholic News Service reports the decision by the Pope means that the diocesan phase of the sainthood process can begin immediately.
Vatican Congregation for Saints' Causes head Cardinal Jose Saraiva Martins said, at a Mass in Coimbra on Wednesday commemorating the third anniversary of Sister Lucia's death, that Pope Benedict had reduced the waiting to three years.
On May 13, 1917, when Sister Lucia was 10 years old, she and her cousins - Francisco, 9, and Jacinta, 7 - claimed to have seen the Virgin Mary at Fatima, near their home.
The apparitions continued once a month until October 1917 and later were declared worthy of belief by the Catholic Church.
In 2000 Pope John Paul II beatified Sister Lucia's cousins, who died as children.
Sr Lucia, who spent most of her life as a Carmelite nun, died at the age of 97 at her convent in Coimbra, near Fatima.
Pope waives wait for Sister Lucia's beatification (Catholic World News 14/02/08)
Pope reduces waiting period for sainthood cause for Fatima visionary
(Catholic News Service 14/02/08)