John Patrick Crichton-Stuart, 3rd Marquess of Bute, KT (12 September 1847 – 9 October 1900) was a Scottish landed aristocrat, industrial magnate, antiquarian, scholar, philanthropist, and architectural patron.

[1] His conversion to Catholicism from the Church of Scotland at the age of 21 scandalised Victorian society and led Prime Minister Benjamin Disraeli to use the Marquess as the basis for the eponymous hero of his novel Lothair, published in 1870.

The 2nd Marquess was an industrialist and began, at great financial risk, the development of Cardiff as a port to export the mineral wealth of the South Wales Valleys.

Accumulating major debts and mortgages on his estates, the Marquess rightly foresaw the potential of Cardiff, telling his concerned solicitor in 1844, "I am willing to think well of my income in the distance."

On 8 December 1868, he was received into the Church by Monsignor Capel at a convent in Southwark, and a little later was confirmed by Pius IX in Rome, resulting in a public scandal.

But at a distance, just over one hundred years from his death, it is his architectural patronage as "the greatest builder of country houses in nineteenth-century Britain"[11] that creates his lasting memorial.

Bute's desires and money allied with Burges' fantastical imagination and skill led to the creation of two of the finest examples of the late Victorian era Gothic Revival, Cardiff Castle[12] and Castell Coch.

Robert Rowand Anderson rebuilt the Georgian Mount Stuart House for him, and Bute worked in collaboration with many of Burges's colleagues, including William Frame and Horatio Walter Lonsdale, on the interiors.

Between 1868 and 1886 he financed the rebuilding of St Margaret's Parish Church, Roath, Cardiff, creating a new mausoleum for the Bute family with sarcophagi in red marble.

The Marquess had been appointed to the board of directors of the Cardiff Savings Bank as "President", at the age of six months, in effect inheriting the office from his father.