Little is known about non-perturbative quantum gravity in de Sitter spacetimes. As a useful low-dimensional model, we consider de Sitter Jackiw-Teitelboim (dS JT) gravity and solve it non-perturbatively in the genus expansion. This amounts to the first non-perturbatively solvable model of de Sitter cosmology. We find that dS JT gravity has an effective string coupling which is pure imaginary, rendering the S-matrix genus expansion Borel resummable. We further establish that dS JT gravity is dual to a formal matrix integral with a negative number of degrees of freedom. More broadly, our analysis unveils new ingredients in the de Sitter holographic dictionary, which may be applicable in more general contexts.