The Indo-Myanmar Ranges (IMR) situated along the plate boundary of India and Eurasia represent the India-Asia suture zone. These mountain ranges were derived in a trench-accretionary system and later exhumed due to changes in wedge dynamics. In NE India, dismembered Neotethyan ophiolites are exposed in the Indian north-eastern states Nagaland and Manipur. It is spread across Phek and Kiphire districts in Nagaland; while in Manipur, it is observed at Ukhrul and Tengnoupal districts. Here, most of the mantle and crustal units of an ideal ophiolite assemblage are recorded except for the sheeted dykes. Ultramafic rocks have been serpentinized to varying extent indicating the role of high water–rock interaction. The source of the serpentinizing fluids could be seawater or fluids dehydrating from the subducting slab. Plagioclase in basalts is albitic in composition due to alteration. Radiometric dating of microfossil assemblages in the flyschoidal and pelagic sedimentary deposits provided concrete evidences in establishing the timings of formation and emplacement of this ophiolite suite. The association of the Neotethyan oceanic lithosphere with the younger flyschoidal deposits and their structural disposition has been presented in this chapter. Mineralization of chromitites, nickel, and sulfides in ultramafic and mafic rocks of the Naga-Manipur ophiolite belt (NMOB) are also documented in this region.