Quick answer
Rei is a girl name.
Meaning and history
From Japanese 鈴 ( rei ) meaning "bell", 麗 ( rei ) meaning "beautiful, lovely" or 玲 ( rei ) meaning "the tinkling of jade". This name can also be formed by other kanji with the same pronunciation.
Notes and context
Usage: japanese | Japanese Hiragana: れい; Japanese Katakana: レイ