Supervised by Peter LeFanu Lumsdaine. We present a formalization of monoids up to coherent homotopy in Agda. In order to achieve this we postulate a structure of type theory with two equalities with a notion of fibrant type. Then we build an operad ∞Mon and define monoids up to coherent homotopy as its algebras. We prove that this notion is invariant under equivalences between fibrant types, and that loop spaces are such monoids.