George Calvert, 1st Baron Baltimore was an English peer and politician. He achieved domestic political success as a member of parliament and later Secretary of State under King James I. He lost much of his political power after his support for a failed marriage alliance between Prince Charles and the Spanish House of Habsburg royal family. Rather than continue in politics, he resigned all of his political offices in 1625 except for his position on the Privy Council and declared his Catholicism publicly. He was created Baron Baltimore in the Peerage of Ireland upon his resignation. Baltimore Manor was located in County Longford, Ireland.

In the Kingdom of England, the title of Secretary of State came into being near the end of the reign of Elizabeth I, the usual title before that having been King's Clerk, King's Secretary, or Principal Secretary.