Details of French royal refugees and Sir Arthur Conan Doyle's family tree are among those made available online for the first time.
Hundreds of volumes of births and baptisms from the Scottish Catholic Archives have been added to the ScotlandsPeople website.
The documents reveal that Conan Doyle (pictured), who never used his baptismal middle name, Ignatius, was born and brought up Catholic at Picardy Place in Edinburgh, though he later renounced religion.
Scotland was home to economic migrants in the early 19th century, when hundreds of skilled craftsmen from France, Spain and Italy arrived to work on building Edinburgh and other cities. The archives show that in the period after the revolution in France, the French royal family were refugees in Scotland and were put up in Holyrood Palace.
The records date from 1703 to 1908 and cover Catholic congregations across Scotland and in the armed forces. They throw important light on the development of Catholic communities, in areas such as Barra and South Uist.
The two-year project adds an extra 143,000 pages and 2 million new names to the 65 million already on the database.
ScotlandsPeople is a partnership between the National Archives of Scotland, the General Register Office for Scotland and the Court of the Lord Lyon. It provides access to digital images of key Scottish family history resources, including more than 60 million birth, marriage and death records, wills, testaments, census records and coats of arms.