BUT or But may refer to:

• "But", a common English conjunction
• British United Traction, a division of Leyland Motors Ltd
• Brno University of Technology, a university located in Brno, Czech Republic
• Bathpalathang Airport, a domestic airport in Bhutan
• "BUT"/"Aisho", a 2007 J-Pop single by Koda Kumi
• But, Opole Voivodeship, a village in Poland
• But (surname)
• For the organic chemical name component, see but-
• BUT (retailer), a French retail store franchise brand

but- is a chemical prefix. It was extracted from "butyric acid". It serves as the number 4 when counting axial atoms in forming names of organic compounds. As an example, butane is an alkane with four carbons.

But/愛証 (BUT/Aishou / BUT/Proof of Love) is Koda Kumi's 35th single and was released on March 14, 2007. It was her first single of 2007 and first to bring her new era, Kingdom. The single was a limited purchase, only being sold from March 2007 to May 2007. It charted #2 on Oricon and stayed on the charts for fourteen weeks. The single was released the same day as her third compilation album, , which was also of limited release.