<jats:title>Abstract</jats:title><jats:p>A new cyclic lipopeptide, marihysin A (<jats:bold>1</jats:bold>), along with the three known cyclodipeptides cyclo(Ala‐Ile) (<jats:bold>2</jats:bold>), cyclo(Ala‐Leu) (<jats:bold>3</jats:bold>), and cyclo(Ala‐Tyr) (<jats:bold>4</jats:bold>), was isolated from the fermentation broth of the marine microorganism <jats:italic>Bacillus marinus</jats:italic> B‐9987 isolated from the tissues of rhizophere of <jats:italic>Suaeda salsa</jats:italic> in the intertidal zone of the Bohai Bay of P. R. China. Marihysin A (<jats:bold>1</jats:bold>) was established to be cyclo(Pro‐Gln‐Asn<jats:sup>1</jats:sup>‐Ser‐Asn<jats:sup>2</jats:sup>‐Tyr‐Asn<jats:sup>3</jats:sup>‐<jats:italic>β</jats:italic>‐aminotetradecanoic acid) by spectroscopic analysis, and it exhibits broad‐spectrum but low activity against plant pathogens as determined by antifungal bioassay.