Itôs an Amaryllis

Called Amaryllis, it's a hybrid Hippeastrum. These grow fantastically well in the ground in Southern California. They like to be dry in the summer, have a rainy winter, then bloom in spring, eventually forming large blooming clumps. Avoid spots that get soggy, otherwise an effortless garden bulb here.

amaryllis ^_^

Hippeastrum correctly, as hoovb said. Known as Amaryllis in the bulb and flower trade but not actually in the genus Amaryllis.