We present the link-calculus, a process calculus based on interactions that are multiparty, i.e., that may involve more than two processes and are open, i.e., the number of involved processes is not xed or known a priori. Communication actions are given not in terms of channels but in terms of chains of links, that record the source and the target ends of each hop of interactions. The semantics of our calculus mildly extends the one of CCS in the version without message passing, and the one of -calculus in the full version. Cardelli and Gordon's Mobile Ambients, whose movement interactions we show to be inherently open multi-party, is encoded in our calculus in a natural way, thus providing an illustrative example of its expressiveness.