Defender of the Faith is a phrase that has been used as part of the full style of many English, Scottish, and later British monarchs since the early 16th century. It has also been used by some other monarchs and heads of state.

James IV was King of Scotland from 11 June 1488 until his death at the Battle of Flodden in 1513. He inherited the throne at the age of fifteen on the death of his father, James III, at the Battle of Sauchieburn, following a rebellion in which the younger James was the figurehead of the rebels. James IV is generally regarded as the most successful of the Stewart monarchs. He was responsible for a major expansion of the Scottish royal navy, which included the founding of two royal dockyards and the acquisition or construction of 38 ships, including the Michael, the largest warship of its time.