Pope Francis signed decrees giving the go-ahead for the honors on the basis of miracles attributed to each candidate, the Holy See said in a statement.
The pope put Paul VI on the path to sainthood by beatifying him in October 2014, while Oscar Romero was likewise elevated to the status of "blessed" in May 2015.
Paul VI completed the reforms of the Second Vatican Council, or "Vatican II," which revolutionized the relationship between Catholic believers and priests and opened the Church to dialogue with other religions.
Mass, historically celebrated in Latin, was translated into local languages and priests addressed their congregations face-on instead of facing the altar.
Paul VI is credited with being one of Pope Francis' role models, a humble man to whom the Argentine pope frequently refers in his speeches. At the beatification mass, Francis had hailed him as a "brave Christian."
Giovanni Battista Montini, a soft-spoken cardinal from northern Italy, was elected pope in 1963, adopting the name Paul VI. He was pope for 15 tumultuous years, which saw many believers and priests leave the Church as social rebellions swept across the West.
His papacy was marked by growing secularization and social liberation, and while the polarized politics of the Cold War did little to ease his task he was also hampered by a reputation for being overly cautious.
He reaffirmed the Church's ban on artificial contraception - despite the fact that his own birth control commission, set up to advise the Vatican, voted overwhelming to lift the prohibition.
The decision enraged many Catholics at a time when believers were embracing sexual freedom and women were demanding the right to use the birth control pill.
Romero, murdered in 1980, was beatified in San Salvador, the capital of El Salvador in Central America, in front of 200,000 worshippers.