The Hoggar region is known to be a zone where the upper mantle exhibits a negative gravity and thermal anomalies. The area is part of a system of large swells over the African continent such as those of: Aïr, Tibesti, Eghei, Darfur and Cameroon mounts. The Hoggar uplift is a broad structure elongated over a 1000 km span in the NE-SW direction. The elevation of the Hoggar is between 500 and 1000 m as a mean with areas where the elevation goes over 2000 m as in Tahat (Atakor, 2150 km2), and Adrar N’ajjer (2500 km2) corresponding to Cenozoic volcanic districts. Several geophysical investigations were conducted to image the lithospheric structure under the Hoggar such as; gravity, magnetic, magnetotelluric, heat flow and seismic tomography. The results obtained over 30 years of investigations, especially the seismic tomography in the region, show traces of a hot spot in the crust and the upper mantle under the Hoggar domal uplift characterized by low P-waves velocity. The seismic tomography revealed that the 4.5° mega-fault is a geological structure that has a deep extent in the lithosphere up to 70 km and also for the Adrar Fault (east of In Ouzzal domain) which is present down to upper mantle. To the north, the Sahara basins (In Salah) exhibit a low-velocity structure that could be associated with a thermal process. There is a good correlation between the zones with low velocity and the volcanic districts in the Hoggar and under the Sahara basin. Regarding the geodynamics of the African plate, it seems that the hot spot responsible for the uplift of the Hoggar could be located nowadays probably 400 km SW of the Tamanrasset.