This chapter explores the relationship between fiduciary law and equity, focusing on an idea that largely determines the place of fiduciary law in private law: that fiduciary law is equitable. In this regard, the term “equitable” implies that fiduciary law serves a characteristic equitable function, a function that solves problems of high variability and uncertainty through higher-order or metalaw. The prominent role played by second-order law in general and the equitable function in particular is what makes fiduciary law special among areas of private law. This chapter first identifies problems addressed by second-order law, and shows how the fiduciary relationships are equitably second order, especially for trustees, other categorical fiduciaries, and fact-specific fiduciaries. It then considers the duty of loyalty as a second-order duty equitably regulating the performance of primary duties and how fiduciary remedies for breach of fiduciary duty (for example, disgorgement) are equitably second order in a way that many prototypically private law remedies are not. Finally, it examines constructive trusts as a second-order aspect of fiduciary remedies and fiduciary law’s relation to contract law.