Pope Francis is removing the commander of the Swiss Guards, with the pontiff reportedly unhappy at the officer's strict authoritarian style.
The news that Daniel Anrig would not be continuing as commander was published in the Vatican's daily newspaper.
He will leave the Vatican after Christmas at the end of an eight-year stint, and be replaced by his deputy.
Since his election Pope Francis has made efforts to reform the Church and make it more open.
The notice in the L'Osservatore Romano said: "The holy father has ordered that Colonel Daniel Rudolf Anrig end his term on 31 January, at the conclusion of the extension of his mandate."
Col Anrig's approach has riled colleagues, with one Swiss Guard telling Italian media "this is the end of a dictatorship", on news of his departure.
No official reason has been given for the dismissal by the Vatican.
The 110-strong Swiss Guard are responsible for the personal security of the Pope.
They have served the papacy for five centuries, first coming to Rome to protect Pope Julius II in 1506.
Analysis: The BBC's David Willey in Rome
Pope Francis, according to Vatican sources, is unhappy at the Swiss officer's excessively strict military discipline imposed on his non-commissioned officers and men.
Colonel Anrig was head of a criminal investigation team in Switzerland before his appointment by former Pope Benedict in 2006.
He was investigated by the Swiss Red Cross and by Amnesty International for alleged human rights violations during a raid he led on an immigrants' refugee centre in 2003, but has denied any wrongdoing.
Pope Francis is apparently also unhappy at the commander's refurbishment of a large and luxurious penthouse apartment for his family above the barracks inside the Vatican where the Swiss Guards are quartered.
The Pope has a relaxed relationship with his security staff, knows most of them by name, and often accepts only reluctantly the advice of those who warn him of possible dangers to his life from lax security arrangements.