We consider semigroups such that the universal left congruence ω is finitely generated. Certainly a left noetherian semigroup, that is, one in which all left congruences are finitely generated, satisfies our condition. In the case of a monoid the condition that ω is finitely generated is equivalent to a number of pre-existing notions. In particular, a monoid satisfies the homological finiteness condition of being of type left-FP 1 exactly when ω is finitely generated.Our investigations enable us to classify those semigroups such that ω is finitely generated that lie in certain important classes, such as strong semilattices of semigroups, inverse semigroups, Rees matrix semigroups (over semigroups) and completely regular semigroups. We consider closure properties for the class of semigroups such that ω is finitely generated, including under morphic image, direct product, semi-direct product, free product and 0-direct union. Our work was inspired by the stronger condition, stated for monoids in the work of White, of being pseudo-finite. Where appropriate, we specialise our investigations to pseudo-finite semigroups and monoids. In particular, we answer a question of Dales and White concerning the nature of pseudo-finite monoids.Lemma 2.5 Let S be a semigroup and let ω S be finitely generated by H ⊆ S 2 . Suppose ω S = K for some K ⊆ S 2 . Then there exists a finite subset K of K such that ω S = K .Further, if there exists m ∈ N such that for any a, b ∈ S, there is an H -sequence from a to b of length at most m, then there is an m ∈ N such that for any a, b ∈ S, there is a K -sequence from a to b of length at most m .Proof The first statement is well known, but we give a short proof here for completeness and convenience.We are given that ω S = H = K . Let (h, k) ∈ H . Then there is a K -sequence of length n := n(h, k) h = t 1 c 1 , t 1 d 1 = t 2 c 2 , . . . , t n d n = k,
