A relative pronoun is a pronoun that marks a relative clause. An example is the word which in the sentence "This is the house which Jack built." Here the relative pronoun which introduces the relative clause, which modifies the noun house. A relative pronoun plays the role of a noun phrase within that clause. For example, in the relative clause "which Jack built," "which" is a pronoun functioning as the object of the verb "built."

In the English language, the following are the most common relative pronouns: which, who, whose, whom, whoever, whomever, and that, though some linguists analyze that in relative clauses as a conjunction / complementizer.

For more information on the formation and uses of relative clauses—with and without relative pronouns—see Relative clause. For detailed information about relative clauses and relative pronouns in English, see English relative clause.