William Isaac Blanchard (died 1790) was an English stenographer.
Blanchard was the grandson of a French refugee, who resided in England. He became a professional shorthand writer, and practised his art in Westminster Hall from 1767 till his death in 1796. His offices were at 4 Dean Street, Fetter Lane, and 10 Clifford's Inn.
He was the inventor of two separate and distinct systems of stenography, the first of which he published under the title of 'A Complete System of Shorthand, being an improvement upon all the authors whose systems have yet been made public; is easy to be attained, and may be read again at any distance of time with the greatest certainty; it being properly adapted to the Latin tongue, and all sorts of technical terms, will make it extremely useful for law, physic, or divinity,' Lond. 1779, 8vo, 16 pp. and two plates. This was followed by the explanation of a much more elaborate system in 'The Complete Instructor of Shorthand, upon principles applicable to the European languages; also to the technical terms used by anatomists, and more comprehensive and easy to write and to read than any system hitherto published,' Lond. 1786, 4to. The method of stenography described in this last work was never practised to any extent, and it certainly does not deserve the extravagant praise bestowed upon it by the author of the 'Historical Account of Shorthand,' which passes under the name of James Henry Lewis. Several trials taken in shorthand by Blanchard were published between 1775 and 1791, including the trials of Admiral Keppel and Horne Tooke.
"Blanchard, William Isaac". Dictionary of National Biography. London: Smith, Elder & Co. 1885–1900.