Old Mortality is one of the Waverley novels by Walter Scott. Set in south west Scotland, it forms, along with The Black Dwarf, the 1st series of his Tales of My Landlord (1816). The novel deals with the period of the Covenanters, featuring their victory at Loudoun Hill (also known as the Battle of Drumclog) and their defeat at Bothwell Bridge, both in June 1679; a final section is set in 1689 at the time of the royalist defeat at Killiecrankie.

Scott's original title was The Tale of Old Mortality, but this is generally shortened in most references.

On 30 April 1816 Scott signed a contract with William Blackwood for a four-volume work of fiction, and on 22 August James Ballantyne, Scott's printer and partner, indicated to Blackwood that it was to be entitled Tales of My Landlord, which was planned to consist of four tales relating to four regions of Scotland. In the event the second tale, Old Mortality, expanded to take up the final three volumes, leaving The Black Dwarf as the only story to appear exactly as intended. Scott completed The Black Dwarf in August, and composed Old Mortality during the next three months.

Scott was steeped in 17th-century literature, but among the printed sources drawn on for The Tale of Old Mortality the following may be singled out for special mention:

Old Mortality appeared as the second, third, and fourth volumes of Tales of My Landlord, published by Blackwood's in Edinburgh on 2 December and by John Murray in London three days later. As with all the Waverley novels before 1827 publication was anonymous. The title-page indicated that the Tales were 'collected and arranged by Jedediah Cleishbotham', reinforcing the sense of a new venture moving on from the first three novels with 'the Author of Waverley' and his publishers, Archibald Constable in Edinburgh and Longman, Hurst, Rees, Orme, and Brown in London. The print run was 2000 copies, and the price £1 8s (£1.40). Two further editions with minor changes followed in the next two months. There is no clear evidence for authorial involvement in these, or in any of the novel's subsequent appearances except for the 18mo Novels and Tales (1823) and the 'Magnum' edition. Some of the small changes to the text in 1823 are attributable to Scott, but that edition was a textual dead end. In October 1828 he provided the novel with an introduction and notes, and revised the text, for the Magnum edition in which it appeared in February to April 1830 as part of the ninth volume, the whole of the tenth, and part of the eleventh.

The standard modern edition, by Douglas Mack, was published with Scott's apparently preferred title "The Tale of Old Mortality", as Volume 4b of the Edinburgh Edition of the Waverley Novels in 1993: this is based on the first edition with emendations from manuscript and the editions immediately following the initial publication; the Magnum material appears in Volume 25a.

After an Introduction to the Tales of My Landlord, supposedly written by the novel's (fictional) editor Jedediah Cleishbotham, the first chapter by the (fictional) author Peter Pattieson describes Robert Paterson ('Old Mortality'), a Scotsman of the 18th century, who late in life decided to travel around Scotland re-engraving the tombs of 17th-century Covenanter martyrs. Pattieson describes at length meeting Robert Paterson, hearing his anecdotes, and finding other stories of the events to present an unbiased picture.

The novel then describes a wapenshaw held in 1679 by Lady Margaret Bellenden, life-rentrix of the barony of Tillietudlem. This was a show of her support for the Royalist cause, but most of her tenants favoured the opposing Covenanters (who wanted the re-establishment of presbyterianism in Scotland) and she has to enlist her unwilling servants. After her supporters are duly mustered, the main sport is a shoot at the popinjay in which the Cavalier favourite is narrowly defeated by Henry Morton, son of a Covenanter. He is introduced to Lady Margaret and her lovely granddaughter Edith Bellenden, with whom he is in love.