The Sabaeans were a people who lived in what is today Yemen in the final millennium BCE. They may be the same nation as the biblical Sheba. They made substantial profits off the spice trade, and left behind many inscriptions in the musnad (Old South Arabian) alphabet.
They were polytheistic, and should not be confused with the Sabians mentioned in the Qur'an, whose name is written with the Arabic letter sad rather than sin, and is widely believed to refer to the Mandaeans.
"Surely they that believe, and those of Jewry, and the Christians and those Sabians, whoso believe in God and the last day, and work righteousness, their wage awaits them with the lord, and no fear shall be on them, neither shall they sorrow" Quran 2:62
The Sabaeans were an ancient people speaking a South Semitic language who lived in what is today Yemen and for a time in northern Ethiopia and Eritrea.
In the 1st century BC it was conquered by the Himyarites, but after the disintegration of the 1st Himyarite empire of the Kings of Saba' and dhu-Raydan the Middle Sabaean Kingdom reappeared in the early 2nd century CE.
The Sabaeans, as were the other Arabian and Yemenite kingdoms of the same period, were involved in the extremely lucrative spice trade, especially frankincense and myrrh.