Common Era (also Current Era or Christian Era), abbreviated as CE, is an alternative designation for the calendar era originally introduced by 6th-century Christian monk Dionysius Exiguus, traditionally identified with Anno Domini (abbreviated AD). Dates before the year 1 CE are indicated by the use of BCE, short for Before the Common Era (likewise with CE, also Before the Current Era or Before the Christian Era). Neither designation uses a year zero, and the two designations are numerically equivalent; thus "2012 CE" corresponds to "AD 2012" and "399 BCE" corresponds to "399 BC".

The expression "Common Era" can be found as early as 1708 in English, and traced back to Latin usage among European Christians to 1615, as vulgaris aerae, and to 1635 in English as Vulgar Era. At those times, the expressions were all used interchangeably with "Christian Era", and "vulgar" meant "not regal" rather than "crudely indecent". Use of the CE abbreviation was introduced by Jewish academics in the mid-19th century. Since the later 20th century, use of CE and BCE has been popularized in academic and scientific publications, and more generally by publishers emphasizing secularism or sensitivity to non-Christians.