P21 (disambiguation)

p21 is a cyclin-dependent kinase inhibitor.

P21 or P-21 may also refer to:

Proteins

 * p21/ras, part of the RAt Sarcoma family of proteins
 * Transforming protein p21, encoded by the HRAS gene in humans

Vessels

 * ARA King, a minelayer and patrol ship of the Argentine Navy
 * HMS Oberon (P21), a submarine of the Royal Navy
 * LÉ Emer (P21), a patrol vessel of the Irish Navy
 * MALTESE PATROL BOAT P21, of the Armed Forces of Malta

Other uses

 * Curtiss XP-21, an American experimental fighter aircraft
 * P21 road (Ukraine)
 * Papyrus 21, a biblical manuscript
 * Yao language
 * Partnership for 21st Century Skills; see 21st century skills
 * Prophet 21, Distribution Software for businesses published by Epicor