At common law, a debenture is any document that either creates or acknowledges an existing debt (Handevel Pty Ltd v Comptroller of Stamps (Vic) (1985) 157 CLR 177; [1985] HCA 73).

In the context of the law relating to corporate fundraising, a debenture of a body corporate is a chose in action that includes an undertaking by that body corporate to repay as a debt money deposited with or lent to the entity (section 9, Corporations Act 2001 (Cth) (CA 2001)). It may include a security interest over property of the body corporate to secure repayment of the money (section 9, CA 2001). There are a number of exceptions to this definition, set out in the CA 2001.