Sir John Joseph Caldwell Abbott PC KCMG QC (March 12, 1821 – October 30, 1893) was a Canadian lawyer and politician who served as the third prime minister of Canada from 1891 to 1892.

Abbott involved himself in politics from a young age, signing the Montreal Annexation Manifesto in 1849 – which he later regretted – and winning election to the Legislative Assembly of the Province of Canada in 1860.

A telegram leaked from his office played a key part in the Pacific Scandal of 1873, which led to the downfall of John A. Macdonald's first government.

Their eldest surviving son, William Abbott, married the daughter of Colonel John Hamilton Gray, a Father of Confederation and premier of Prince Edward Island.

[5] In 1849 he was a signatory to the Montreal Annexation Manifesto, calling for union of the Canadas with the United States, resulting in the withdrawal of his commission in the militia.

[5] His recruitment of a battalion of 300 men, known as the 11th Argenteuil Rangers, during the Trent Affair of 1861 may have been designed to atone for what he later described as the “sins of youth” and to enhance his political credentials, as much as to express his concern for his country's safety.

[6] He commanded the regiment on the border multiple times throughout the Fenian Raids, on March 8, 1866, they were called out for active service and were stationed in various villages throughout Argenteuil.

[7] On June 11, 1866, the Rangers were called out to serve at Cornwall, and then Saint-Jean-sur-Richelieu, and a reporter from Montreal stated: "I learned on Sunday afternoon that troops were to be sent to St. Johns [Saint-Jean] by special train; and managed to procure permission to come out with them.

In 1849, he signed the Montreal Annexation Manifesto calling for Canada to join the United States, an action which he regretted later as a youthful error.

He served as solicitor general for Lower Canada (Quebec) representing the liberal administration of John Sandfield Macdonald and Louis Sicotte, from 1862 until 1863.

[10] His proposal to protect the electoral borders of 12 English Quebec constituencies was eventually incorporated into the British North America Act, 1867.

As legal advisor to its main financier, Sir Hugh Allan, Abbott was the recipient of the infamous telegram from Prime Minister Macdonald during the 1872 Canadian federal election campaign which read "I must have another ten thousand; will be the last time of calling; do not fail me; answer today."

Abbott was subsequently a key organizer of a second syndicate which eventually completed the construction of Canada's first transcontinental railway in 1885, serving as its solicitor from 1880 to 1887 and as a director from 1885 to 1891.

He was one of just two Canadian Prime Ministers, the other being Mackenzie Bowell, to have held the office while serving in the Senate rather than the House of Commons.

Despite the political toll on his party, Abbott dealt with the backlog of government business awaiting him after Macdonald's death, including reform of the civil service and revisions of the criminal code.

One year into his time as prime minister, Abbott attempted to turn the office over to Thompson, but this was rejected due to anti-Catholic sentiment in the Tory caucus.

[10] Suffering from the early stages of cancer of the brain, Abbott's health failed in 1892 and he retired to private life, whereupon Sir John Thompson finally became prime minister.