Saint Katherine protectorate is one of the most floristically diverse spots in the Middle East. A field surveys, as well as critical revision of herbarium specimens, were carried out during 2013-2020 revealed that 430 taxa belonging to 283 genera and 62 families. The life-forms are classified into seven life forms with dominance of Therophytes (39%) followed by Chamaephyte (24.7%). Chorological study indicated that 52% of recorded taxa were mono-regional native to Saharo – Arabian (29%), Irano- Turanian (10.39%), Mediterranean (7.4%), Sudanin (4%) while tropical and sub- tropical represented by (0.2%) only. 223 taxa were mono-regional, 127 taxa were bi-regional, while 16 taxa were endemic and Steno-endemic. Investigated taxa distributed in four microhabitats; terraces, slopes, gorges, and wadi bed the last two were the most diversity. The present study investigated that presence of Papaver somniferum is a new record to flora of Egypt, eight new records to Sinai and thirty four new records to the study area.