| Prince of Colonna |
|Spouse||Princess of Colonna|
|Behind the scenes|
|Appearances||"The Adventure of the Six Napoleons"|
The Prince of Colonna was an Italian nobleman and the rightful owner of the Borgia Pearl, a black gem considered by Sherlock Holmes to be the most famous of its kind in the world. He is mentioned in "The Adventure of the Six Napoleons", in connection with two of Holmes' cases.
The first time Holmes' path crossed the Prince was when the Borgia Pearl was stolen from the Prince's rooms while he was staying at the Dacre Hotel in London. The pearl's disappearance caused a sensation, and Holmes himself consulted on the case alongside Scotland Yard. The prime suspect in the theft was the Princess' maid, Lucretia Venucci, who was rumored to have a brother in London. However, the investigation was in vain.
A year later, however, Holmes found the pearl while investigating a seemingly unrelated case of a madman smashing busts of Napoleon. The pearl was discovered to have been hidden in one such bust by Beppo, who had worked at the factory that produced them. In the end it is not revealed whether Holmes returned the pearl to the Prince (he simply tells Watson to "put the pearl in the safe"), but presumably he did.
- The Colonna family was a powerful Italian noble family that exercised great influence over Medieval and Renaissance Rome. The family supplied many high church officials and political figures, including one pope, and maintained a three-century long feud with the Orsini family over influence in Rome. They were granted a princely title by Pope Pius IX in 1854.