Yersiniabactin (Ybt), the siderophore produced by Yersinia pestis, has been crystallized successfully in the ferric complex form and the crystal structure has been determined. The crystals are orthorhombic with a space group of P2(1)2(1)2(1) and four distinct molecules per unit cell with cell dimensions of a=11.3271(+/-0.0003)A, b=22.3556(+/-0.0006)A, and c=39.8991(+/-0.0011)A. The crystal structure of ferric Ybt shows that the ferric ion is coordinated as a 1:1 complex by three nitrogen electron pairs and three negatively charged oxygen atoms with a distorted octahedral coordination. The molecule displays a Delta absolute configuration with chiral centers at N2, C9, C10, C12, C13, and C19 in R, R, R, R, S, S configurations, respectively. Few of the crystal structures of siderophores have been solved, and those which have been are of simple hydroxamate and catechol types such as ferrioxamine B and agrobactin. To our knowledge this is the first report of the ferric crystal structure of 5-member heterocycle siderophore.