Catholicism does not recognise divorce and teaches marriage is a lifelong commitment.
In order to separate, Catholics must have their marriage annulled by showing it was flawed from the outset.
The radical reforms allow access to procedures free of charge and fast-track decisions.
Until now the procedures have been seen as arcane, expensive and bureaucratic.
Catholics seeking an annulment previously needed approval from two Church tribunals. The reforms will reduce this to one and remove the requirement of automatic appeal. An appeal will still be possible if one of the parties requests it.
The new fast-track procedure will allow bishops to grant annulments directly if both spouses request it.
Because annulment procedures are complicated, couples normally require experts to guide them through, meaning that gaining one can be expensive.
Without an annulment, Catholics who divorce and marry again are considered adulterers and are not allowed to receive communion.
Last year, the Pope set up a commission of church lawyers and clerical experts to look at how to streamline the procedure.
Writing about the changes, Pope Francis said it was unfair that spouses should be “long oppressed by darkness of doubt” over whether their marriages could be annulled.
“This move is in accord with the Pope’s oft-repeated image of the Church as a ‘field hospital’ that goes out to meet people where they are most in need, and then to treat their most serious wounds first — rather than stay at home and wait for people to come to them,” said the Rev. James Bretzke, an expert on papal affairs at Boston College.
One prominent Catholic priest, Lames Martin, called Tuesday’s announcement “an act of mercy from a pastoral Pope who listens carefully to the concerns of the people.”
In June, the Pontiff said “there are cases when separations are inevitable. Sometimes they can even become morally necessary.”