Ultramafic intrusion is found in Selen Wuha area of Raya marginal graben. Selen Wuha arearnis located 600km away from Addis Ababa to the northern Ethiopia. Some of the previousrnresearchers were considered it as basement low grade metamorphic unit while others have notrnconformed to this idea and considered is as young aged un-metamorphosed igneous intrusion.rnThus, the target of this study is to resolve this gap by characterizing the intrusion using fieldrnobservation, petrography and geochemical data. The study area covers about 20km2 and it hasrnmapped with the scale of 1:25,000. Accordingly, ultramafic unit, plagioclase-olivine phyricrnbasalt, pyroclastic material and alluvial sediment deposit are recognized major mappablernunits. Moreover, small intrusions (dykes), normal faults, lineaments, joints and veins arernidentified geologic structures of the area. Hence, the contact of ultramafic with adjacent unitsrnis controlled by tectonic contacts. Minerals in the ultramafic are coarse grained Cpx, Opx, Olrnand Fe-Ti oxide. Similarly, minerals in gabbroic units are coarse grained plag, Cpx, Ol andrnFe-Ti oxides. Texturally, both units are porphyritic-phaneritic in which the size of grains isrnrange from medium pheneritic to coarse pheneritic. Plagioclase-olivine phyric basalt hasrnporphyritic texture in which Ol and plag are the dominant phenocryst minerals. Based on thernproportion of Ol, Pxn, and concentration of MgO, the studied ultramafic unit is classified intornpyroxenite and peridotite. Since any sign of metamorphism is not found in the unit, it is anrnigneous intrusion which has intruded in early Cenozoic formations and Mesozoic sedimentaryrnsuccessions. Accordingly, the studied ultramafic unit is not Neoproterozoic in age however itrnis Cenozoic aged intrusion. From the geochemistry point of view, the ultramafic unit isrnderived from depleted mantle source since it shows high concentration of MgO (22.31 wt. %rnto 37.08 wt. %), Mg # (72.63 to 81.94), Cr (1690ppm to 3000ppm), Ni (1030ppm torn1980ppm) and Co (96ppm-143ppm). It shows also slight depleted in LREE and very lowrnconcentration of the highly incompatible trace elements. Furthermore, the samples are cogenetic,rnsourced from homogeneous source and related by fractional crystallization since theyrnshow good correlation in the selected major oxide and trace element variation diagrams.