Fra' Galeas von Thun und Hohenstein (24 September 1850 – 26 March 1931) was the Prince and Grand Master of the Sovereign Military Order of Malta from 1905 to 1931.

He was born in Trento (then in Austria, now in Italy), the youngest son of Count Guidobald Maria Thun und Hohenstein and of his wife, Teresa Guidi dei Marchesi di Bagno.

[1] On 8 June 1875 Thun und Hohenstein was admitted to the Sovereign Military Order of Malta as a Knight of Justice.

[2] In 1885 he became the representative of the Grand Priory of Bohemia and Austria at the Order's headquarters in Rome; it was at this time that he gave up his position in the Austrian civil service.

He continued to be Grand Master, but a Lieutenant, Fra' Pio Franchi de' Cavalieri, acted on his behalf.