The Baden 9 Kreuzer Error (German: Baden-Fehldruck 9 Kreuzer) is a postage stamp error produced by the historical German state of Baden in 1851.

The green color was intended for the 6 Kreuzer value, but apparently, the paper sheets were mismatched.

The cancellations recorded have the numbers "4" for Achern, "41" for Ettenheim, and "106" for Orschweier (today Mahlberg).

The 9 Kreuzer error was not discovered until 44 years after the stamp was issued.

It must be assumed that the printer had unintentionally used the wrong plate for the green paper: instead of a "9" he had read a "6".