Motivated by the recent realization of hyperbolic lattices in circuit quantum electrodynamics, we exploit ideas from Riemann surface theory and algebraic geometry to construct the first generalization of Bloch band theory to hyperbolic lattices, which can be formulated despite the absence of commutative translation symmetries. For an arbitrary Hamiltonian with the symmetry of a {4g, 4g} tessellation of the hyperbolic plane, we produce a continuous family of eigenstates that acquire Bloch-like phase factors under the Fuchsian group of the tessellation, which is discrete but noncommutative. Quasi-periodic Bloch wavefunctions are then generalized to automorphic functions. Naturally associated with the Fuchsian group is a compact Riemann surface of genus g 2, arising from the pairwise identification of sides of a unit cell given by a hyperbolic 4g-gon. A hyperbolic analog of crystal momentum continuously parametrizes a discrete set of energy bands and lives in a 2g-dimensional torus, which is a maximal set of independent Aharonov-Bohm phases threading the 2g noncontractible cycles of the Riemann surface.This torus is known in algebraic geometry as the Jacobian of the Riemann surface. We propose the Abel-Jacobi map -which associates to each point of the Riemann surface a point in the Jacobian -as a hyperbolic analog of particle-wave duality. Point-group symmetries form a finite group of automorphisms or self-maps of the Riemann surface and act nontrivially on the Jacobian. The tight-binding approximation and Wannier functions are also suitably generalized. In genus 1, our theory reduces to known band theory for 2-dimensional Euclidean lattices. We demonstrate our theory by explicitly computing hyperbolic Bloch wavefunctions and bandstructures numerically for a regular {8, 8} tessellation associated with a particular Riemann surface of genus 2, the Bolza surface.