Sir Geoffrey Adams Dinwiddie Johnstone, KCMG (born 19 September 1927 in Nassau) is a Bahamas politician and lawyer. He is the eldest son of the late Bruce Eric Johnstone and Wilhelmina Helena Aline Johnstone née Kemp. Johnstone was born in Nassau on 19 September 1927.
He graduated from Queen’s College, Nassau, Bahamas, and upon graduation from that institution in September 1945, he worked as an insurance agent for British American Insurance Company Ltd. for two years. In 1947, he enrolled in the Inns of Court School of Law. He was called to the Degree of the Utter Bar at the Middle Temple in June 1950. He continued to practice law until he retired in December 1998.
In August 1950, he joined the firm of Higgs & Johnson and was admitted to partnership in 1952. He became Senior Partner of Higgs & Johnson in 1968 and continued until his retirement in 1998.
He served as President of the Bahamas Bar Association from June 1973 to June 1975 and as Vice President from June 1975 to June 1976.
He has served as an Elder of St. Andrew’s Presbyterian Kirk since April 1963 and continues in that office. In November 2010, at the celebration of the Kirk's 200th Anniversary, he received an achievement award for outstanding service to the Kirk and its mission.
He took an early interest in politics after his return from his studies abroad. He was elected to the House of Assembly for the Eastern District of New Providence in November 1962 and served that constituency until January 1967 when he was returned as the Member for the Montagu Constituency where he served until September 1972.
He served in the United Bahamian Party Cabinet as Minister of Road Traffic and Records from January 1964 to January 1967. In February 1970, he was appointed Leader of the Opposition and served in that office until July 1971.
He served as Chairman of the Hotel Corporation of The Bahamas from October 1992 to December 1994, during which period the Corporation was very involved in the privatization of its hotels.
He was appointed a Commander of the Most Distinguished Order of St. Michael and St. George (CMG) by Her Majesty Queen Elizabeth II on 31 December 1994.
He has also served as Deputy to the Governor General of The Commonwealth of The Bahamas on various occasions. In July 1995, he was appointed non-resident Ambassador of The Bahamas to Chile, Argentina and Uruguay.
In the birthday honours of Her Majesty Queen Elizabeth II on 31 December 2002, there was conferred on him the dignity of a Knight Commander of the Most Distinguished Order of St. Michael and St. George (KCMG).
His hobbies include boating, fishing and shooting.