This is a tough question. The exact number isn’t known.
For the first 1,500 hundred years of the Church, a saint was anyone who died for the Faith or attracted devoted followers after death. The very first official, pope-canonized saint was Ulric of Augsburg in 993, but before and after that, the majority were unofficially recognized and venerated.
It was not until the 17th century that Pope Urban VIII clarified that only the Holy See had the authority to canonize a saint. From that time on, requirements were gradually added to the canonization process regarding things such as local veneration and acclaimed miracles. Such processes are important to guarantee authenticity.
There appear to be about 11,000 saints (around 1,600 of them officially canonized by the new process) but no one can say for sure because no one really kept track of them all for a long time.
By the time the process was established, there were many saints canonized according to the earlier standards. Furthermore, there are holy men and women who die in sanctity, but whose lives were hidden—no one on earth could have known that they died saints!
We joyfully honor all the saints whose names we do know—and those we don’t—in a special way on All Saints Day! But let’s make a practice of seeking saintly intercession every day. Here at The Catholic Company, we’ve created a Saints Alphabet Magnet Set of canonized holy men and women (plus a few beloved Marian titles!). Teach your children about sanctity from A to Z with this exclusive set of delightfully illustrated magnets. Available today at The Catholic Company!