Rule 34 is an Internet meme that states "If it exists, there is porn of it. No exceptions."

Rule 34 may also refer to:

• Rule 34 (film), a 2022 film directed by Julia Murat
• Rule 34 (novel), a 2011 novel by Charles Stross
• "Rule 34", a 2014 episode of comedy television series Garfunkel and Oates
• Rule 34 of the Federal Rules of Civil Procedure, which governs requests for production of documents
• Rule 34, the Wolfram code for a particular elementary cellular automaton

• The 34th Rule, a 1999 Star Trek: Deep Space Nine novel