Anna Masterton Buchan (24 March 1877 – 24 November 1948) was a Scottish novelist who wrote under the pen name O.
She attended Hutchesons' Grammar School in Glasgow, but lived most of her later life in Peebles in the Scottish border country, not far from the village of Broughton where her parents first met.
Unforgettable, Unforgotten (1945) is a memoir of her brother John, Lord Tweedsmuir, and the Buchan family.
Her work is displayed alongside her brother's at the John Buchan Museum in Peebles.
[5] This was to be the hallmark of all her fiction, gently humorous domestic dramas with little if any reference to political events or social change.