Sir Raja Sonam Topgay Dorji (CIE) (Dzongkha:སྟོབས་རྒྱས་རྡོ་རྗེ་; Wylie transliteration: Stobs-rgyas Rdo-rje) (1896–1953), also called Tobgay, was a member of the Dorji family and Bhutanese politician who served between 1917 and 1952 in the Royal Government under the First and Second Kings of Bhutan. During this period, Topgay Dorji officially held the posts of Gongzim (Chief Minister), Deb Zimpon (Chief Secretary), and Trade Agent to the Government of Bhutan. As such, Topgay Dorji was responsible for fostering Anglo-Bhutanese relations, and later, Bhutan–India relations. Topgay's ties with the west and modernist political factions contributed significantly to the modern political landscape and modernization of Bhutan.
Topgay Dorji inherited his positions from his father, Kazi Ugyen Dorji, who was instrumental in advising Ugyen Wangchuck before and after he became the First King of Bhutan. Topgay Dorji lived, worked, and died at Bhutan House, the Dorji's estate in Kalimpong, India, the traditional administrative center of southern Bhutan.
Topgay was the son of Gongzim Ugyen Dorji, adviser to Ugyen Wangchuck both before and after the rise of the latter to the throne. Gongzim Ugen Dorji had advised the future First King to mediate between the British and Tibet, and later to allow the large-scale induction of Nepalis into Bhutan establishing friendly ties with British India.