XX or xx most often refers to:
20 (number), Roman numeral XX
XX or xx may also refer to:
Genetics An organism with two X chromosomes, in the XY sex-determination system (of humans, as well as some other animals and some plants) and the XO sex-determination system (of some animals): Usually female, producing ova gametes that fuse with the male gamete during sexual reproduction XX male syndrome (AKA de la Chapelle syndrome), a rare congenital intersex condition
Arts and media Music
Bands The xx, an English indie rock band X_______X (band), an American no wave band
Albums
Toto XX, by Toto, 1998 XX (Mushroomhead album), 2001 xx (The xx album), 2009 XX (Great Big Sea album), 2012 XX – Two Decades of Love Metal, by HIM, a 2012 compilation album XX (O.A.R. album), 2016 XX (Mino album), 2018 XX (Note-oriety album), 2018 [+ +], a 2018 EP by Loona, repackaged as [X X] or [× ×] in 2019 XX (Brian Culbertson album), 2020 XX (Il Divo album), 2024 XX (Fally Ipupa album), 2026
Songs "xx", from Expectations (Hayley Kiyoko album), 2018 "XX", from Ferxxo (Vol 1: M.O.R) by Feid, 2020
Other uses in arts and media XX (film), a 2017 anthology horror movie "XX" (CSI), a 2004 episode (S4 E17 / #86) of CSI: Crime Scene Investigation XX (web series), a 2020 South Korean online television drama XX (organization), a fictional organisation in the XIII comics (adapted into a video game, film, and TV series) XX (novel), 2020, by Rian Hughes Les XX, a group of twenty Belgian painters The Seeds of Death, a 1969 Doctor Who serial (production code XX)
Military XX System or Double-Cross System, a British deception operation in the Second World War XX Bomber Command, an inactive US Air Force unit XX Corps (disambiguation) , a legion of the Roman Empire
Computing xx, to express exponentiation in the initial version of the FORTRAN programming language .xx ("dot ex ex"), a placeholder for an Internet country code top-level domain
Other uses Dos Equis or Siglo XX, a brand of Mexican beer
See also XX gonadal dysgenesis, a type of female hypogonadism resulting in non-functioning ovaries
Ex-ex-gay, a social movement United States Exploring Expedition of 1838–1842 to the Pacific Ocean and surrounding lands Ex Ex Lovers, a 2025 Philippine romantic comedy film 20 (disambiguation) Double Cross (disambiguation) X (disambiguation) XXX (disambiguation) XXXX (disambiguation)