It was established in 1821 as the School of Arts of Edinburgh, the world's first mechanics' institute, and was subsequently granted university status by royal charter in 1966.

Having been inspired by Anderson's College in Glasgow, Horner established the school to provide practical knowledge of science and technology to Edinburgh's working men.

[8][9]: 64–66  The institution was initially of modest size, giving lectures two nights a week in rented rooms[10] and it had a small library of around 500 technical works.

[8] The school was managed by a board of eighteen directors[8] and primarily funded by sponsors from the middle and upper classes, including Robert Stevenson and Walter Scott.

[9]: 103  "In 1837, the School of Arts moved to leased accommodation on Adam Square, which it purchased in 1851 with funds raised in Watt's name.

[11] Heriot-Watt's time as the Watt Institution marked a transitional period for the organisation, as its curriculum broadened to include several subjects beyond mathematics and the physical sciences.

[9]: 133–135 A shifting class make-up was not the only demographic change to affect the student body: in 1869 women were permitted to attend lectures for the first time.

[12]: 163  The decision to admit women was made in large part owing to pressure from local campaigner Mary Burton, who later became the institution's first female director in 1874.

The move caused the institution severe financial difficulties, which were compounded by a combination of declining funds from subscribers and increased costs from its growing student body.

The proposed merger was provisional to changes in the structure of the Watt Institution, which would see the organisation become a technical college with representatives of the Trust in management positions.

[15] After the establishment of Heriot-Watt as a technical college, the new management committee set about extending the institution's buildings and strengthening its academic reputation.

[16] Expansion meant that the college made increasing demands on George Heriot's Trust throughout the first part of the 20th century, which ultimately led to the independence of the two bodies in 1927.

While the Trust continued to pay Heriot-Watt a fixed sum each year, from then on the college was responsible for managing its own financial affairs.

During World War I, student numbers dropped as young men joined the army, while teaching in engineering stalled as the department was used for the manufacture of shells and munitions.

[9]: 213–215  During World War II, student numbers dropped again and the electrical engineering department became involved in training the armed services in the use of radar.

[17] While Heriot-Watt continued to expand in the centre of Edinburgh after attaining university status, the institution had grown big enough that relocation was felt to be desirable.

[16] In 1966 Midlothian County Council gifted the Riccarton estate north of Currie to the university, and in 1969 work began on transforming the site into a future campus.

[23] However, in 2017 it was also announced that a major budget shortfall and the impact of Brexit would result in Heriot-Watt shedding 100 jobs by voluntary redundancies.

It was ranked 11th place in the UK for art and design in the 2013 Complete University Guide,[29] produced a winner and five other finalists for the Scottish Fashion Awards Graduate of the Year in June 2012.

As well as its own library, accommodation and catering facilities,[31] it has its own branch of the Student Union which runs events on the site[32] and is home to a collection of textile records and artefacts.

[5] Offering a range of undergraduate and postgraduate courses similar to those found in Scotland, the campus facilitates student exchanges between Britain and the Gulf Emirates.

[40] The new campus was officially opened by King Charles III on 30 November 2023, accompanied by Scotland’s First Minister, Humza Yousaf.

[42] Heriot-Watt's campus in Stromness, Orkney, is home to the International Centre for Island Technology (ICIT), part of the university's School of Energy, Geoscience, Infrastructure and Society.

[59] In 2011, Heriot-Watt was named as The Sunday Times Scottish University of the Year 2011–2012, with the paper emphasising the employability of the institution's graduates.