Debussy was associated with various French composers whose work stylistically spanned nineteenth-century tradition to the twentieth-century avant-garde. This chapter explores his connections with Ernest Guiraud, Ernest Chausson, Camille Saint-Saëns, Gabriel Fauré, Paul Dukas, and Erik Satie. It assesses key issues in each setting. Various relationships are represented here: the student-teacher archetype, less formalised mentorship, peer friendships, the more distant collegial relationship, and sometimes adversarial exchanges. Debussy and these composers engaged with each other in multiple ways; dynamics shifted such that the student became the teacher, a distant figure became a colleague, a peer became a critic. The study of these relationships casts new light on Debussy and the other parties.