Fouldes v Willoughby (1841) 8 M&W 540 is a leading English law case on the tort of conversion.

The judge at the trial told the jury that the defendant ferryman, by taking the horses from the plaintiff and turning them out of the vessel, had been guilty of a conversion.

The Exchequer Court held that the ferryman was not guilty of conversion, because there was no interference with the plaintiff's "general right of dominion" over the horses.

“In my opinion,” said Lord Abinger CJ, “he should have added to his direction, that it was for them to consider what was the intention of the defendant in so doing.

It has never yet been held that the single act of removal of a chattel, independent of any claim over it, either in favour of the party himself or any one else, amounts to a conversion of the chattel.” Rolfe B gave a now well recognised definition of conversion that it is, "a taking with the intent of exercising over the chattel an ownership inconsistent with the real owner's right of possession".