Mount Clare, also known as Mount Clare Mansion and generally known today as the Mount Clare Museum House, is the oldest Colonial-era structure in Baltimore, Maryland, U.S. The Georgian style of architecture plantation house exhibits a somewhat altered five-part plan.

The structure was built in 1763 on a Carroll family plantation by barrister Charles Carroll the Barrister, (1723–1783), a descendant of the last Gaelic Lords of Éile in Ireland and a distant relative of the much better-known Charles Carroll of Carrollton, (1737–1832), longest living signer of the Declaration of Independence and the richest man in America in his later years, also the layer of the First Stone of the new Baltimore and Ohio Railroad, just a short distance away in 1828.

The City of Baltimore purchased a large portion of the former estate in 1890 as its third large landscaped park. Mount Clare has been maintained by the National Society of Colonial Dames in Maryland, the local chapter of The National Society of The Colonial Dames of America, since 1917. In 1970, it was added to the National Register of Historic Places and was designated a National Historic Landmark for its architecture.

Mount Clare features a portico on the front façade with a projecting bay above. The upper bay contains a Palladian window. The City of Baltimore built Palladian pavilions connected by hyphens on either side in 1910 as a concealed public toilets structure, but these do not reflect historical construction that were originally on the estate. They have since been converted to a library and a colonial-era kitchen exhibit. A circa 1912 stable, once used to house the horses of the city's park rangers, has been restored and is now used for classroom space as well as a rental facility for events and meetings.

The first building on the Mount Clare property was built by John Henry Carroll, Charles Carroll's brother, (1723–1783), in 1754, and was probably eventually incorporated into the larger house. Charles inherited the property after John's death. The property consisted of 800 acres from the much larger Georgia Plantation, which had belonged to their father, Dr. Charles Carroll. Mount Clare overlooked the northwestern shore of Ridgely's Cove of the Middle Branch and Ferry Branch of the Patapsco River, where some wharves and docks existed along with the Baltimore Iron Works, one of the largest industrial enterprises of colonial America. Charles began construction of the house between 1757 and 1760.

This area had originally been near the first selected site by the appointed town commissioners for the new Baltimore Town, laid out in 1729. A different location, further northeast on the Basin, head of the Northwest Branch of the Patapsco River, was chosen after the landowner John Moale objected to the project on the theory that he had located important iron ore deposits there that he intended to eventually mine and exploit. One hundred and twenty years earlier, during the first explorations and mapping by the famed Captain John Smith, (1580–1631), of the northern Chesapeake Bay, on his 1608 map he had labeled what is now called the Patapsco River as Bolus River, from the Latin word meaning clay, usually holding iron mineral deposits.

Charles Carroll the Barrister, (1723-1783), began building the present 2+1⁄2-story Georgian style central block, incorporating his brother John's kitchen and flanking it with a wash house and an orangery. In 1768, Charles added the projecting bay and Palladian window that dominate the entry facade today. The kitchen wing was enlarged and an office wing was added for balance, resulting in a symmetrical nine-part elevation. The house was completed about 1767.

After Barrister Charles' death in 1783, his widow made further changes, connecting the outbuildings and adding a greenhouse to the orangery and expanding the laundry, resulting in a complex about 360 feet long. These additions, along with other alterations, were in the more current style of Federal architecture which is similar to but slightly different from the older Georgian.