The Rat or Mouse is the first of the repeating 12-year cycle of animals which appear in the Chinese zodiac, constituting part of the Chinese calendar system. The Year of the Rat in standard Chinese is Chinese: 鼠年; pinyin: shǔnián. The rat is associated with the first branch of the Earthly Branch symbol 子 (zǐ), which starts a repeating cycle of twelve years. The Chinese word shǔ refers to various small rodents (Muroidea), such as rats and mice. The term "zodiac" ultimately derives from an Ancient Greek term referring to a "circle of little animals". There are also a yearly month of the rat and a daily hour of the rat. Years of the rat are cyclically differentiated by correlation to the Heavenly Stems cycle, resulting in a repeating cycle of five years of the rat, each rat year also being associated with one of the Chinese wu xing, also known as the "five elements", or "phases": the "Five Phases" being Fire, Water, Wood, Metal, and Earth.

The Chinese zodiac is a traditional classification scheme based on the Chinese calendar that assigns an animal and its reputed attributes to each year in a repeating twelve-year cycle. In traditional Chinese culture, the Chinese zodiac is very important and exists as a reflection of Chinese philosophy and culture. Chinese folkways held that one's personality is related to the attributes of their zodiac animal. Originating from China, the zodiac and its variations remain popular in many East Asian and Southeast Asian countries, such as Japan, South Korea, Vietnam, Singapore, Nepal, Bhutan, Cambodia, and Thailand.