Torgny Torgnysson Segerstedt (11 August 1908, Mellerud, Dalsland – 28 January 1999) was a Swedish philosopher and sociologist. He was the son of the elder Torgny Segerstedt, scholar of comparative religion and publicist remembered especially for his uncompromising anti-Nazi stance. To distinguish him from his father, when needed, he is often referred to as Torgny T:son Segerstedt (i.e. Torgny T[orgnys]son Segerstedt), or Torgny Segerstedt the younger.
The younger Torgny Segerstedt was born in Mellerud, Holm parish, Älvsborg County, but the family was actually living in Lund at the time, where the elder Torgny Segerstedt taught at the university. He grew up in and from 1917, when his father became editor of Göteborgs Handels- och Sjöfartstidning (GHT), in Gothenburg.
After completing his secondary education at Göteborgs högre samskola, Segerstedt matriculated at Lund University in 1927, and, after receiving his Licentiate in 1931 and some time in Paris and London, completed his Ph.D. in practical philosophy in 1934. After a few years teaching in Lund, he received the chair of philosophy in Uppsala in 1938, switched to a new chair in sociology in 1948, and served as rector magnificus of the university from 1955 to 1978. He was a member of numerous academies and learned societies, including the Swedish Academy from 1975. On June 2, 1978 Segerstedt received an honorary doctorate from the Faculty of Pharmacy at Uppsala University, Sweden.