Michel Talagrand played a decisive role in the transformation of mean-field spin glass theory into a rigorous mathematical subject. This chapter offers a narrative account of that development. We begin with the physical origins of the Sherrington-Kirkpatrick (SK) model and the emergence of the TAP and Almeida-Thouless stability frameworks, culminating in Parisi's replica symmetry breaking (RSB) ansatz and its hierarchical order parameter. We then review early rigorous milestones, including high-temperature results and stability identities, and describe the consolidation of interpolation and cavity methods through the work of Guerra and of Aizenman-Sims-Starr. The central event in this narrative is Talagrand's 2006 proof of the Parisi formula for the SK model and for a broad class of mixed $p$-spin models, and his subsequent analysis of Parisi measures. We also discuss Talagrand's later program constructing pure states under extended Ghirlanda-Guerra identities and an atom at the maximal overlap, together with the structural results that followed, notably Panchenko's ultrametricity theorem and extensions of the Parisi formula. Throughout, we indicate how related contributions by many authors fit into the same long-running program across probability, analysis, and mathematical physics.