Isidor George Beaver (December 1859 – 24 October 1934), often misspelled "Isidore" and frequently initialized as "J. G. Beaver", was an architect from England who had a substantial career in Adelaide, South Australia and Melbourne, Victoria. He was significant in the early history of ice skating in Australia.
Isidor Beaver was a son of Louis Beaver (c. 1819–1879) of Manchester. He emigrated to Australia, and in 1884 had an office on Victoria Square, Adelaide. H. E. Fuller served his articles with him for four years from 1884. He joined with partners Edmund Wright and James Henry Reed to form Wright, Reed & Beaver. In 1886 their design for the Jubilee Exhibition Building was awarded second prize. In 1889 they won a design contest for the National Mutual Life Association's new Melbourne premises at the south-west corner of Queen and Collins Streets, and set up offices in Queen Street, headed by Beaver, to oversee the project, of eight storeys, later known as Goode House, and now the home of the Bank of New Zealand Australia.
The partnership was dissolved in 1893, and Beaver remained in Melbourne with offices at 125 Queen Street. In 1894 he relocated to the Fourth Victoria Building, 243 Collins Street. R. H. Solly trained as a junior under Beaver and was for four years his chief draftsman before becoming an architect with Wunderlich Ltd. (who had offices in the same building). In 1901 his office was located at 11 Elizabeth Street then moved to Altson's Buildings, 82 Elizabeth Street, on the Collins Street corner. In 1915 Arthur William Purnell joined him to form the partnership Beaver & Purnell which lasted until 1925.