Plain clothes or Plainclothes may refer to:

• Plainclothes law enforcement
• Plain Clothes (1925 film), a silent black and white short American film
• Plain Clothes (1988 film), an American comedy film
• Plainclothes (film), 2025 American film
• Plain Clothes Theatre Productions, a theatre company based in Bristol, England
• Plainclothes (TV series), a 1990s New Zealand crime drama series
• Plain dress, a religious practice of wearing clothes of traditional, modest design