Sigma, founded in 1922 as Sigma Theta Tau International, is the international honor society of nursing. It recognises nursing students and practising nurses for scholarship, leadership and service, and reports more than a million members, over 600 chapters and a presence in more than 100 countries.
The Greek letters stood for the words for love, courage and honour. The organisation shortened its public name to Sigma as it became less exclusively American.
How membership works
Membership is by invitation rather than application. Students are invited on academic standing, and practising nurses are invited as community leaders who have demonstrated achievement in nursing. Induction happens through a local chapter, usually attached to a school of nursing, and members keep the affiliation for life.
The credential most people encounter is the set of letters after a nurse's name. Membership is an honour rather than a licence or a certification: it does not authorise anything and does not appear in state regulation. See nursing specialties for the difference between licensure, certification and recognition.
What it does
Beyond induction, Sigma funds and disseminates nursing research, publishes scholarship including a leading nursing journal and a large catalogue of books, runs leadership development programmes, and maintains a repository of nursing research and dissertations.
Its foundation funds small research grants, which matter more in nursing than the amounts suggest, because nursing research has historically been funded at a fraction of medical research and early-career nurse researchers often have no other route to a first grant.
Its place in the profession
Sigma sits alongside the American Academy of Nursing as one of the two main honorific bodies in American nursing, and the two are frequently confused. The academy elects fellows for sustained national contribution, principally in policy and research; Sigma inducts far more people, far earlier in their careers, on scholarship and leadership potential.
Neither confers authority. Both are signals used in academic and leadership hiring, which is why they appear in the credential strings on faculty and executive profiles. See the nurse faculty shortage.
Related
- Nursing organizations
- Nursing specialties
- The nurse faculty shortage
- Nursing theory
- History of nursing
Sources
- About Sigma. Sigma, for the 1922 founding, membership, chapters and mission. Accessed September 9, 2026.