詹姆斯·普雷斯科特·焦耳，FRS（James Prescott Joule；1818年12月24日－1889年10月11日），英国物理学家。他出生于曼彻斯特近郊的索尔福德。焦耳在研究热的本质时，发现了热和功之间的转换关系，并由此得到了能量守恒定律，最终发展出热力学第一定律。国际单位制导出单位中，能量的单位——焦耳，就是以他的名字命名。他和开尔文合作发展了温度的绝对尺度。他还观测过磁致伸缩效应，发现了导体电阻、通过导体电流及其产生热能之间的关系，也就是常称的焦耳定律。

James Prescott Joule FRS (/dʒuːl/; (24 December 1818 – 11 October 1889) was an English physicist and brewer, born in Salford, Lancashire. Joule studied the nature of heat, and discovered its relationship to mechanical work (see energy). This led to the law of conservation of energy, which led to the development of the first law of thermodynamics. The SI derived unit of energy, the joule, is named after James Joule. He worked with Lord Kelvin to develop the absolute scale of temperature the kelvin. Joule also made observations of magnetostriction, and he found the relationship between the current through a resistor and the heat dissipated, which is now called Joule's first law.