Rose Mackenberg (July 10, 1892 – April 10, 1968) was an American investigator specializing in fraudulent psychic mediums, known for her association with Harry Houdini. She was chief of a team of undercover investigators who investigated mediums for Houdini in the 1920s. After Houdini's death, she continued to investigate spiritualist fraud for over 20 years and was known as an expert on the subject. She testified in court cases and before Congress and was interviewed in national magazines and on television.

Mackenberg was born July 10, 1892, and lived in Brooklyn, New York City. In her early years she worked as a stenographer in a law office and as an investigator in New York City. She reportedly believed that psychics and fortunetellers were able to communicate with spirits and foretell the future.

In the early 1920s, Mackenberg was working on a case for a banker who had suffered losses after making investments on the advice of a psychic medium. She sought Houdini's help in the case, as he was very publicly engaged in a campaign against false mediums.

Impressed with Mackenberg, Houdini educated her on the tricks that mediums use to manipulate their victims. In 1925, Houdini hired her as part of his undercover investigator team. The team included several other women such as Houdini's niece Julia Sawyer and a showgirl named Alberta Chapman. Men on the team included Clifford M. Eddy, Jr., Robert H. Gysel, and Amadeo Vacca.

While Houdini was on tour in 1925 and 1926, Mackenberg and the other investigators would precede him by up to 10 days into each city to perform undercover investigations of the local spiritualists or psychic mediums. To remain undercover, they used various disguises and false names, some of them containing puns like "Frances Raud" (for FRAUD) and "Alicia Bunck" (for All Is A Bunk). Mackenberg sometimes wore a hearing aid she didn't need. Her very detailed written reports for Houdini have been studied and exhibited in museums.

Mackenberg appeared on stage with Houdini in many tour stops, including Indianapolis, Worcester, Mass. Washington, D.C. Chicago, New York and Montreal. When Houdini performed in each city, he would debunk local mediums from the stage, presenting the gathered evidence. Houdini and his investigators became the target of great anger from the spiritualists. It was said he carried a Derringer and he advised Mackenberg to carry a gun as well, but she refused.

Mackenberg earned the respect of Houdini and his team and was considered his chief investigator. The other investigators sometimes called her "The Rev" because of the multiple bogus spiritualist diplomas and titles she had acquired during her investigations. Prior to his death, Houdini set up secret codes with more than twenty friends to attempt to communicate with them from beyond the grave. Mackenberg was among those chosen, and in 1945 she reported "the message has not come through."

Mackenberg decided, after Houdini's unexpected death, to carry on the investigations alone.