Lord Pingyuan (平原君; ca. 308–251 BC), born Zhao Sheng (趙胜), was a prominent nobleman and chancellor of the State of Zhao during the Warring States period of ancient China, and one of the Four Lords of the Warring States. He was a son of King Wuling of Zhao, and served as chancellor in the courts of his brother King Huiwen (r. 298–266 BC) and his nephew King Xiaocheng (r. 265–245 BC). Lord Pingyuan was celebrated for his role in lifting Qin's siege of the Zhao capital Handan, thus saving Zhao from annihilation. However, his chancellorship also saw the crushing defeat of Zhao by Qin at the Battle of Changping, which led to the siege. As with the rest of the Four Lords, his generosity to his retainers is considered a major part of his political and diplomatic accomplishments.