Wolff, Gustav Wilhelm (1834–1913), shipbuilder, businessman, and politician, was born in Hamburg, the son of Moritz Wolff and Fanny Maria Schwabe. Gustav left home at the age of fourteen to study engineering at Liverpool College, staying with his uncle Gustav Schwabe. He was subsequently apprenticed to the Manchester engineering firm of Joseph Whitworth & Company, which he represented at the Paris Exhibition of 1855. He worked briefly as a draughtsman for B. Goodfellow Limited of Hyde, before being appointed personal assistant to Edward Harland (qv) at Queen's Island, Belfast, in 1857. He had not been long at Belfast before Harland sent him off on one of Schwabe's steamers to learn more about marine engineering. When Harland took over the yard in 1858, Wolff was appointed chief draughtsman and in 1861 joined him as a partner in the firm of Harland & Wolff. His role in the business was to manage the drawing office and the engine works. By the early 1870s he had relinquished these responsibilities, devoting his time to the critical role of developing the relationship with his uncle's expanding shipping interests. In 1873 he became a partner in the newly established Belfast Ropework Company, no doubt to secure supplies for the yard. Together with W. H. Smiles (qv), the eldest son of the famous social reformer Samuel Smiles, he devoted much of his energy to developing the business, becoming its first chairman. He kept in close touch with his parents in Hamburg: Smiles and his wife recalled visiting him in Hamburg at the home of his parents whom they described as ‘good kindly folk’ (Smiles, 158).
A bachelor, Wolff became an enthusiastic admirer of Belfast, living at Strandtown in a house he named The Den. Although he was of Jewish descent, he became a member of the Church of Ireland, giving generously towards the building of St Anne's cathedral at the turn of the century. He supported many charities, particularly the Ulster Hospital for Women and Children, and the Orange Order.
He and Harland both withdrew from the partnership in 1884, but Wolff remained much more closely involved than Harland in the affairs of the business. He made an extensive tour of India in 1887–8 in the company of the founder of the White Star Line, Thomas Ismay, and his wife. In 1892 he entered parliament as conservative member for East Belfast, retaining his seat in the general election later in the year. In the house of commons Harland and he were soon nicknamed Majestic and Teutonic after two liners they had recently built for the White Star Line. Gaining a reputation as a good constituency MP, he held his seat unopposed until he stood down at the 1910 general election.
Gustav Schwabe, then aged seventy-nine, transferred many of his business interests to his nephew in 1893. This allowed Harland & Wolff to win business from the Hamburg–Amerika Line controlled by Albert Ballin, to whom Schawbe seems to have been related. The following year Wolff acquired an interest in the Union Steamship Company which ran services to southern Africa. He visited the ports in the region before approving the designs for new tonnage to be built at Queen's Island.
When William Pirrie (qv), who was effectively managing director of Harland & Wolff, became lord mayor of Belfast in 1896, Wolff had to devote more time to the business. Shortly before Sir Edward Harland's death in 1895, he had quipped: ‘Sir Edward Harland builds the ships for our firm, Mr Pirrie makes speeches; and, as for me, I smoke the cigars’ (H. Jefferson, Viscount Pirrie of Belfast, 59). This was far from the truth and he remained an important contact with shipowners and potential financiers. When the Union Line merged with Sir Donald Currie's Castle Mail Packets Company to form the Union Castle Line in 1900, Wolff kept his seat on the board and helped to maintain the association with the shipbuilding yard. He finally relinquished his direct interest in Harland & Wolff in 1906, selling his shares to Pirrie, but continued to provide considerable loan capital until his death. After his retirement he lived almost exclusively at 42 Park Street, his London home, rarely visiting Belfast, but keeping in contact with his Hamburg relations. He died there on 17 April 1913 and was buried in Brompton cemetery. He never married.