exclusive distributorship agreement; sole sales contract
A legal or business term for a contract granting one party the exclusive right to sell a product or service in a defined territory or market.
Our company entered into an exclusive distributorship agreement for that product.
独占販売契約 is a near-synonym also meaning exclusive sales contract, but 一手販売契約 emphasizes the sole agency aspect (一手 = 'one hand'), while 独占販売契約 stresses monopoly (独占 = 'monopoly').
Compound of 一手 (いって, 'one hand; sole') + 販売 (はんばい, 'sales') + 契約 (けいやく, 'contract'). The term is a straightforward business compound with no obscure historical derivation.