A generalized modular relation of the form F (z, w, α) = F (z, iw, β), where αβ = 1 and i = √ −1, is obtained in the course of evaluating an integral involving the Riemann Ξ-function. It is a two-variable generalization of a transformation found on page 220 of Ramanujan's Lost Notebook. This modular relation involves a surprising generalization of the Hurwitz zeta function ζ(s, a), which we denote by ζw(s, a). While ζw(s, 1) is essentially a product of confluent hypergeometric function and the Riemann zeta function, ζw(s, a) for 0 < a < 1 is an interesting new special function. We show that ζw(s, a) satisfies a beautiful theory generalizing that of ζ(s, a) albeit the properties of ζw(s, a) are much harder to derive than those of ζ(s, a). In particular, it is shown that for 0 < a < 1 and w ∈ C, ζw(s, a) can be analytically continued to Re(s) > −1 except for a simple pole at s = 1. This is done by obtaining a generalization of Hermite's formula in the context of ζw(s, a). The theory of functions reciprocal in the kernel sin(πz)J2z(2and Jz(x), Yz(x) and Kz(x) are the Bessel functions, is worked out. So is the theory of a new generalization of Kz(x), namely, 1Kz,w(x). Both these theories as well as that of ζw(s, a) are essential to obtain the generalized modular relation.