Mwendojoto (kwa Kiingereza: en:Thermodynamics) ni tawi la fizikia linalohusika na moto na halijoto katika uhusiano na nishati na kazi. Tabia zake zinafuata kanuni nne za mwendojoto, bila kujali mata husika. Mwendojoto hutumika katika mada nyingi za sayansi. Ugunduzi wa sheria mpya za joto (mwendojoto) ulitokana na juhudi kubwa za uchunguzi katika kipindi cha mapinduzi ya viwanda kutokana na kuongezeka kwa kiasi kikubwa kwa mahitaji ya nishati, hasa kwa mchango wa mwanafizikia Mfaransa Nicolas Léonard Sadi Carnot (1824). Scottish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 Clausius, Rudolf (1850). On the Motive Power of Heat, and on the Laws which can be deduced from it for the 'Theory of Heat'. Poggendorff's Annalen der Physik, LXXIX (Dover Reprint). ISBN 978-0-486-59065-3.  William Thomson, LL.D. D.C.L., F.R.S. (1882). Mathematical and Physical Papers 1. London, Cambridge: C.J. Clay, M.A. & Son, Cambridge University Press, 232.  (1993) The Refrigerator and the Universe. Harvard University Press. ISBN 978-0-674-75325-9. OCLC 32826343.