Zhang Zai (張載; 1020–1077) was a Chinese Neo-Confucian moral philosopher and cosmologist.

Zhang Zai was born in 1020 CE in Hengqu, province of Shaanxi. In his childhood he showed interest in military affairs, but began to study the Confucian texts. Like many Song philosophers, Zhang was initially frustrated with Confucian thought and studied Buddhism along with Daoism for a number of years. But, he decided that "The Way" could not be found in Buddhism or Daoism and resorted back to Confucian texts. His exploration of diverse religious thought had a major impact on his own ideals. In 1056 CE Zhang lectured on the Classic of Changes, which would be known as one of his most memorable works. It is suspected that around this time Zhang had first met the Cheng brothers. After passing the highest level of the civil service examinations, he held several minor government posts.

In 1069 CE Zhang was suggested to the emperor and given a place in the capital's government, but not long after he ran into disagreement with the prime minister and retired to his home Hengqu, where he spent his time studying and teaching. This was likely the most productive period of his life for developing and spreading his own philosophical views. In 1076 CE he finished his most significant work, Correcting Ignorance, and presented it to his disciples. Later in 1076 CE he was summoned back to the capital and restored to a high ranked position. However, in the winter he became sick and was forced to resign again. He never reached his home town of Hengqu, dying on the road in 1077. Zhang was enshrined in the Confucian temple in 1241 for his work. Many of Zhang's writings have been lost. Zhu Xi collected selections of Zhang's writings in his anthology of Song Study of the Way known as Reflections on Things at Hand. His most important surviving works are probably his commentary on the Changes and Correcting Ignorance.