Let S 0 , S 1 and S 2 be connected Riemann surfaces and let β 1 : S 1 → S 0 and β 2 : S 2 → S 0 be surjective holomorphic maps. The associated fiber product S 1 × (β 1 ,β 2 ) S 2 has the structure of a singular Riemann surface, endowed with a canonical map β to S 0 satisfying that β j • π j = β, where π j is coordinate projection onto S j . In this paper we provide a Fuchsian description of the fiber product and obtain that if one the maps β j is a regular branched cover, then all its irreducible components are isomorphic. In the case that both β j are of finite degree, we observe that the number of irreducible components is bounded above by the greatest common divisor of the two degrees; we study the irreducibility of the fiber product. In the case that S 0 = C, and S 1 and S 2 are compact, we define the strong field of moduli of the pair (S 1 × (β 1 ,β 2 ) S 2 , β) and observe that this field coincides with the minimal field containing the fields of moduli of both pairs (S 1 , β 1 ) and (S 2 , β 2 ). Finally, in the case that the fiber product is a connected Riemann surface, we provide an isogenous decomposition of its Jacobian variety.