The Heguanzi, an eclectic, composite work arguably of the late Warring States to Han period, has long been associated with a school of thought known as Huang-Lao. Unfortunately, little was known about the school until the recent Mawangdui discovery of four ancient treatises commonly referred to as the Silk Manuscripts of Huang-Lao (Huang-Lao Boshu). This article examines the relation between the Heguanzi and Huang-Lao thought as represented in the Silk Manuscripts. The author argues that many of the chapters of the Heguanzi display key features of Huang-Lao thought, most notably a commitment to foundational naturalism and natural law that is first articulated in mature form in the Silk Manuscripts.