Shai Hermesh was born in Tel-Aviv in 1944.
He graduated from Tichon Hadash high-school and his military service was spent first in the Nahal brigade, and later in the paratroops brigade. As a member of the "Yegev" core of the Ha'Noar Ha’Oved (Labor Party youth movement), he joined Kibbutz Kfar Azza, on the Gaza Strip border.
Shai Hermesh is married to Hava, a teacher who specializes in computers, and is a father to 4 boys and a girl!
He earned a B.A. degree in economics and sociology and later an MBA in Business Management, both from the Hebrew University of Jerusalem. His doctoral studies in Jewish history at Tel-Aviv University, under the supervision of Prof. Anita Shapira, were not completed, since in late 1987 he was asked to serve as Mayor of the Sha’ar Hanegev Regional Council and Chair of the Executive Committee at the Negev College – later to become Sapir Academic College.
For 25 years, Shai has served in the military reserve in the paratroops brigade. In the Six Day War, he took part in the battle for Jerusalem, fought in the Yom Kippur War on the Suez Canal, and in Lebanon - in the 1982 Lebanon War.
Shai Hermesh has filled a range of public positions: he is a member of the National Security Council, the Broadcasting Authority Forum, the Negev Development Authority, leadership institutions of the Kibbutz Movement, the Histadrut leadership, as well as being an active director in several public companies.
He served as the mayor of the Sha’ar Hanegev regional council for fifteen years. During his terms of office, he worked to enlarge the Pinchas Sapir College of the Negev, and to establish the Sapir Academic College, which is now Israel’s largest regional college.
As mayor of the regional council and chair of Sapir College, Shai Hermesh formed close ties with Jewish communities in Europe and the USA that donated generously and helped build the college, in particular and encourage settlement along the Gaza Strip in general.
Shai Hermesh worked in tandem with "Amdocs" - one of the world’s leading software houses, to create a major development center – "Amdocs Negev" – in Sha'ar Hanegev/Sderot.
Until the outbreak of the Intifada in 2000, he worked to promote joint regional-development programs with the Palestinians in the Gaza Strip – such as founding an industrial park, utilizing sewage in moshavim, and programs to train professional personnel for the Palestinian Authority in courses at the college and in Gaza.
For six straight years the regional council, under Shai’s leadership, won the Gold Prize – a prize awarded by the Minister of the Interior for excellence in financial management.
Shai Hermesh was awarded the State of Israel’s Knight of Quality Government award, an award conferred by the Movement for Quality Government in Israel, for setting a personal example as a public personage heading a regional community, attentiveness to national goals, outstanding financial management in a harsh economic climate, developing general and academic education, and for contribution to klitat aliya.
In June 2002, Shai Hermesh was elected Treasurer of the Jewish Agency.
In May 2006 he took his seat in the Israeli Knesset, as a member of the Kadimma party.