 After a brief introduction, this entry begins with Spinoza’s views on the distribution of modal properties (section 2). With respect to substances (2.1), Spinoza claims that every possible substance necessarily exists. Spinoza’s argument for this conclusion is part of his larger argument for substance monism—the view that only one substance exists, God. Spinoza’s view about the modal status of modes, his other main ontological category, is far more controversial (2.2). Explaining this controversy leads into the heart of Spinoza’s metaphysics and involves his views on causation, inherence, God, ontological plenitude and the principle of sufficient reason. Although the question of whether Spinoza was a necessitarian is the predominant topic of discussion in the recent secondary literature on Spinoza’s modal views, Spinoza also sketches interesting accounts of the nature of modality (section 3) and the ground of modality (section 4) that shed fresh light on his modal commitments. Though understudied by recent interpreters, these topics were of interest to Spinoza’s peers and remain vibrant research questions in contemporary metaphysics of modality.