Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Lochlainn O Raifeartaigh (11 March 1933 18 November 2000) was an Irish physicist of worldwide repute in the field of theoretical particle physics. He is best known for the O'Raifeartaigh Theorem, an important result in unification theory, and the O'Raifeartaigh Model of supersymmetry breaking. O'Raifeartaigh was born in Dublin in 1933, and most of his scientific career was centred around that city, where he obtained his first degrees at University College Dublin (BA in 1953 and MSc in Mathematical Physics in 1956), and spent from 1968 until his death as Senior Professor at the Dublin Institute for Advanced Studies.