middleman

US /ˈmɪdlˌmæn/

・

UK /ˈmɪdlmæn/

Someone who buys many goods and resells to others
A person who facilitates a transaction or negotiation between two parties.
A person who acts as an intermediary or go-between, especially in commercial dealings.
A person who goes between buyers and sellers.
A person who tries to settle a disagreement.
A person who profits unfairly from a transaction.
A distributor or other intermediary in a supply chain.

Examples

He acts as middleman for companies seeking contracts abroad.

The firm sells through a middleman because it does not have its own sales force.