In U.S. criminal law, a proffer agreement, proffer letter, proffer, or "Queen for a Day" letter is a written agreement between a prosecutor and a defendant or prospective witness that allows the defendant or witness to give the prosecutor information about an alleged crime, while limiting the prosecutor's ability to use that information against him or her.^[1]

As part of the agreement, the subject may agree to create a statement, known as a proffer statement, setting out their testimony. A meeting in which proffer agreements and statements are negotiated or set out is called a proffer session.^[2] The proffer testimony may be recorded as video evidence, in which case it is known as a proffer video.^[3]

Examples of proffer agreements include:

• According to the New York Times, Rudy Giuliani made a proffer agreement with U.S. federal prosecutors in 2023^[4]
• Kenneth Chesebro made a proffer agreement with prosecutors in the state of Georgia in 2023 in relation to the Georgia election racketeering prosecution.^[5] Jenna Ellis and Sidney Powell made proffer videos in the same case.^[3]
• Duane 'Keefe D' Davis made a proffer agreement in 2009 in regard to the death of Tupac Shakur^[6]