Duplex, meaning double or twofold, commonly refers to:

• Duplex (building), a two-unit apartment building or condominium
• Duplex (telecommunications), a telecommunications systems where signal can flow in both directions between connected parties

Duplex can also refer to:

Arts and music

• Duplex (film), a 2003 movie starring Ben Stiller and Drew Barrymore
• Duplex (band), a Dutch electronic music duo
• Duplex! (Canadian band), a Canadian children's music band
• The Duplex, a comic strip by Glewewedwrwers

Other

• Duplex can refer to a double stranded molecule of DNA or RNA
• Duplex can refer to a type of stainless steel
• Duplex can refer to double-sided printing, Duplex printing