Sierra Leone
27 April 1961 (from UK)

Singapore
9 August 1965 (from Malaysian Federation)

Slovakia
1 January 1993 (Czechoslovakia split into the Czech
Republic and Slovakia)

Slovenia
25 June 1991 (from Yugoslavia)

Solomon Islands
7 July 1978 (from UK)

Somalia
1 July 1960 (from a merger of British Somaliland, which
became independent from the UK on 26 June 1960, and Italian
Somaliland, which became independent from the Italian-administered
UN trusteeship on 1 July 1960, to form the Somali Republic)

South Africa
31 May 1910 (from UK); note - South Africa became a
republic in 1961 following an October 1960 referendum

Spain
the Iberian peninsula was characterized by a variety of
independent kingdoms prior to the Moslem occupation that began in
the early 8th century A. D. and lasted nearly seven centuries; the
small Christian redoubts of the north began the reconquest almost
immediately, culminating in the seizure of Granada in 1492; this
event completed the unification of several kingdoms and is
traditionally considered the forging of present-day Spain

Sri Lanka
4 February 1948 (from UK)

Sudan
1 January 1956 (from Egypt and UK)