Edmund Thomas Blacket (25 August 1817 – 9 February 1883) was an Australian architect, best known for his designs for the University of Sydney, St. Andrew's Cathedral, Sydney and St. Saviour's Cathedral, Goulburn.

Arriving in Sydney from England in 1842, at a time when the city was rapidly expanding and new suburbs and towns were being established, Blacket was to become a pioneer of the revival styles of architecture, in particular Victorian Gothic. He was the most favoured architect of the Church of England in New South Wales for much of his career, and between late 1849 and 1854 was the official "Colonial Architect to New South Wales".

While Blacket is famous for his churches, and is sometimes referred to as "The Wren of Sydney", he also built houses, ranging from small cottages to multi-storey terraces and large mansions; government buildings; bridges; and business premises of all sorts. Blacket's architectural practice was highly influential in the development of Australian architecture. He worked with a number of other architects of both Australian and international importance: James Barnet, William Wardell and John Horbury Hunt. Among his children, Arthur, Owen and Cyril followed him into the profession. The successful architect William Kemp also trained in his practice.

Edmund Blacket is regarded by descendants of the Blackett family as "a man of the strictest probity with a great love for his profession, who also studied the classics, and was considered the leading authority on Classical Greek in Sydney, loved music, playing the organ at the temporary wooden pro-Cathedral, was a competent wood-carver and an amateur mechanical engineer".

Edmund Blacket was born on 25 August 1817 at 85 St Margaret's Hill (later Borough High Street) Southwark, London, England, the seventh child of James Blacket and Margaret Harriot née Ralph. His father was a prosperous draper or slopseller of Smithfield, London. The family were Nonconformists, and Edmund's grandfather Edward Ralph, a former clockmaker, had been minister of a Congregational church at Maidstone. Blacket was educated at Mill Hill School, near Barnet, and although he showed an early interest in architecture, his father opposed him taking up the profession.

On leaving school, Blacket went to work for his father and then at a linen mill in Stokesley, Yorkshire. This mill was owned by his father in partnership with a Thomas Mease and operated by Edmund's brothers John and James. However, the Blackets ended the partnership with Mease in July 1837 as they were unhappy about certain financial matters, and by March 1838, the issue was in Chancery.

In about 1837, although lacking formal training, Blacket began work for the Stockton and Darlington Railway as a surveyor. This was the period of rapid expansion of the railways and in railway engineering and innovation. As a railway surveyor one of Blacket's jobs would have been the design of railway stations. He continued in Yorkshire until 1841, taking every possible opportunity to draw ancient buildings and their details, which included spending his 23rd birthday surveying Whitby Abbey.

Blacket's diaries indicate that he had become a member of the Church of England and had a great love for the Anglican Liturgy. His brother Henry Blackett became a high church Anglican clergyman. Three of Blacket's sketchbooks from this period of the architectural details of buildings in the United Kingdom (1829-1841) are now held at the University of Sydney Library.