Alexandros Papadiamantis (Greek: Ἀλέξανδρος Παπαδιαμάντης; 4 March 1851 – 3 January 1911) was an influential Greek novelist, short-story writer and poet.

Papadiamantis was born in Greece, on the island of Skiathos, in the western part of the Aegean Sea. The island would figure prominently in his work. His father was a priest. He moved to Athens as a young man to complete his high school studies, and enrolled at the School of Philosophy of the University of Athens, but never completed his studies. This happened because he had economic difficulties, and had to find a job to make a living.

He returned to his native island in later life, where he would spend the rest of his life and eventually pass away there in 1911. He supported himself by writing throughout his adult life, anything from journalism and short stories to several serialized novels. From a certain point onwards he had become very popular, and newspapers and magazines vied for his writings, offering him substantial fees. Papadiamantis did not care for money, and would often ask for lower fees if he thought they were unfairly high; furthermore, he distributed his earnings to those who needed it more and took no care of his clothing and appearance. He never married, and was known to be a recluse, whose only true cares were observing and writing about the life of the poor and of spiritual figures, as well as chanting at church: he was referred to as "kosmokalogeros" (κοσμοκαλόγερος, "a monk in the world"). He died of pneumonia.