Let M = { a , b , c , … } and Γ = { α , β , γ , … } be two non-empty sets. M is called a Γ -semigroup if a α b ∈ M , for α ∈ Γ and b ∈ M and ( a α b ) β c = a α ( b β c ) , for all a , b , c ∈ M and for all α , β ∈ Γ . A semigroup can be considered as a Γ -semigroup. In this paper we introduce orthodox Γ -semigroups and extend different results of orthodox semigroups to orthodox Γ -semigroups.