One of the largest medieval shipwreck excavations has been performed in Yenikapi since 2004 and resulted with 37 ships from Byzantine Period. Four of them (YK13, YK16, YK25, YK36) were galleys. Wood of thirteen different plant species was identified using anatomical identification of 619 wood pieces that were collected from the site. In building of planking Pinus nigra Arnold., Cedrus libani A.Rich., and Castanea sativa Mill were used. Platanus orientalis L. and Ulmus L. sp were preferred as floor timber. Keels were Platanus orientalis L. and Quercus L. sp., and treenails were Spartium junceum L. and Quercus sp. Because of wide distribution of these tree species within and northern of the Mediterranean Basin, and also having a common trade of wood of these tree species, the origin of the galleys could not be determined exactly.