An o-mamori (お守り, also お守 and 御守) is an amulet or charm thought to grant the bearer good fortune, good health, or protection.

The o- (お or 御) is an honorific prefix, and mamori comes from the verb mamoru (守る), meaning "to protect".

The first few days of the new year are a time when many people visit a shrine or temple (or both) in a ritual known as Hatsumōde. At larger temples and shrines where amulets are sold, many visitors will pick up an o-mamori for good luck throughout the coming year.

When choosing which o-mamori to buy for yourself or to give to someone, it can be tempting to select an amulet in a favorite color or by some other design element. But o-mamori have different blessings that are indicated by what's written on them, or on signs where they are sold.

Here are some common expressions you might find on o-mamori that, if memorized, might help you avoid such faux pas as giving your prospective father-in-law a charm to help him through childbirth.

Many people will also take an old o-mamori that has protected them over the previous year (or helped them through a strenuous life event) back to the shrine or temple and give thanks for the divine assistance received.