400s may refer to: * The period from 400 to 499, almost synonymous with the 5th century (401–500) * The period from 400 to 409, known as the 400s decade, almost synonymous with the 41st decade (401-410) This disambiguation page lists articles associated with the same title formed as a letter-number combination. If an internal link led you here, you may wish to change the link to point directly to the intended article.