Currently negotiation covers a huge and unstructured domain of negotiation- and coordination protocols and associated strategies. Researchers and practitioners like system engineers have almost no support in discussing protocol solutions to frequently occurring negotiation problems and in designing and implementing successful protocols and associated negotiation media. In this paper we will introduce a pattern language for negotiation protocol solutions and will introduce an online pattern library with a first collection of protocol patterns. The patterns are written from the point of view of a system engineer, but draw on the results of other disciplines such as social choice theory, mechanism design theory or group decision and negotiation theory. Our goal is to enable an interdisciplinary and efficient communication process about successful protocol designs for the most diverse negotiation and coordination situations and to support system engineers in their design decision.