Joshua Johnson was an American painter from the Baltimore area of African and European ancestry. Johnson is known for his naïve paintings of prominent Maryland residents.

It was not until 1939 that the identity of the painter of elite 19th-century Baltimoreans was discovered by art historian and genealogist J. Hall Pleasants, who believed that thirteen portraits were painted by one Joshua Johnson. Pleasants attempted to put the puzzle of Johnson's life together; however, questions on Johnson's race, life dates and even his last name (Johnson or Johnston) remained up until the mid-1990s, when the Maryland Historical Society released newly found manuscripts regarding Johnson's life.

Documents dated from July 25, 1782, state that Johnson was the "son of a white man and a black slave woman owned by a William Wheeler, Sr." His father, George Johnson (also spelled Johnston in some documents) purchased Joshua, age 19, from William Wheeler, a small Baltimore-based farmer, confirmed by a bill of sale dating from October 6, 1764.

Wheeler sold Johnson the young man for £25, half the average price of a male slave field hand at the time. The documents state little of Joshua's mother, not even her name, and she may have been owned by Wheeler, whose own records stated that he owned two female slaves, one of whom had two children.

A manumission was also released, in which George Johnson acknowledged Joshua as his son, also stating that he would agree to free Joshua under the conditions that he either completed an apprenticeship with Baltimore blacksmith William Forepaugh or turned 21, whichever came first. The manumission was signed and confirmed by justice of the peace Colonel John Moale who would, during 1798–1800, commission Joshua to paint a portrait of his wife and granddaughter, Mrs. John Moale and Her Granddaughter, Ellin North Moale (illustrated at left).

Johnson received his freedom in 1782 and began advertising, identifying himself as a portrait painter and limner as of 1796. He moved frequently, residing often where other artists, specifically chair-makers, lived, which suggests that he may have provided extra income for himself by painting chairs. His frequent moving also may suggest that he tended to work for clients near whom he lived. No records mention educational or creative training and it still has not been proven that he had any type of relationship with artists such as the Peale family, Ralph Earl, or Ralph Earl Jr.

Catholic Church records show that in 1785 he married his first wife, Sarah, with whom he had four children – two sons and two daughters, the latter of whom both died young. By 1803 he was married to a woman named Clara. According to the Baltimore city directory of 1817–1818 he was listed in the section "Free Householders of Colour"; in 1825 he had moved to Frederick County, Maryland, and two years later moved to Anne Arundel County, again, following the paths of those whose portraits he painted. Little is known of his life after this final move, and his death.