Abstract: An overfill safety adapter is provide which is suitable for use on the outlet end of funnel like devices being used to transfer fluid from one container to another to prevent the overfill of the container and spilling of the fluid which includes an elongated frusto conical shaped housing member adapted to be releasably fitted within an opening of a container to be filled having a bore therethrough, the bore of the housing having a conically shaped upper portion adapted to be releasably mounted on an outlet end of a funnel or spout and a substantially cylindrically shaped lower discharge portion which slidably supports a float operably responsive to the level of fluid in a container; and a magnetically operative valve within the bore of the housing which magnetically co-acts with the float to close the flow of fluid through the bore responsive to the level of fluid in a container to be filled.