Champerty and maintenance are doctrines in common law jurisdictions that aim to preclude frivolous litigation:

In Giles v Thompson Lord Justice Steyn declared: "In modern idiom maintenance is the support of litigation by a stranger without just cause. Champerty is an aggravated form of maintenance. The distinguishing feature of champerty is the support of litigation by a stranger in return for a share of the proceeds."

At common law, maintenance and champerty were both crimes and torts, as was barratry (the bringing of vexatious litigation). This is generally no longer so as, during the nineteenth century, the development of legal ethics tended to obviate the risks to the public, particularly after the scandal of the Swynfen will case (1856–1864). However, the principles are relevant to modern contingent fee agreements between a lawyer and a client and to the assignment by a plaintiff of his rights in a lawsuit to someone with no connection to the case. Champertous contracts, such as third-party litigation funding agreements, can still, depending on jurisdiction, be void for public policy or attract liability for costs.

The restrictions arose to combat abuses in medieval England. Unscrupulous nobles and royal officials would lend their names to bolster the credibility of doubtful and fraudulent claims in return for a share of the property recovered. Speaking extrajudicially in the early seventeenth century, Lord Chief Justice Coke described the origins of maintenance in this way:

Maintenance, manutenentia, is derived from the verb manutenere, and signifieth in law a taking in hand, bearing up, or upholding of quarrels and sides, to the disturbance or hindrance of common right.

The comments were made in context of the court previously having been anxious to prevent a wide range of maintenance; the term "maintenance" had been used to apply not just to those who gave support in civil claims, but also to those who sought to maintain robbers, heretics and even "a new sect coming from beyond the sea, clad in white garments". Judicial independence was gradually established, however, and by the early 19th century Jeremy Bentham wrote:

A mischief, in those times it seems but too common, though a mischief not to be cured by such laws, was, that a man would buy a weak claim, in hopes that power might convert it into a strong one, and that the sword of a baron, stalking into court with a rabble of retainers at his heels, might strike terror into the eyes of a judge upon the bench. At present, what cares an English judge for the swords of a hundred barons? Neither fearing nor hoping, hating nor loving, the judge of our days is ready with equal phlegm to administer, upon all occasions, that system, whatever it be, of justice or injustice, which the law has put into his hands.

In Australia, champerty and maintenance as common law causes of action (as either a crime or a tort) have mostly been abolished by statute. In New South Wales, champerty and maintenance were abolished by the Maintenance, Champerty and Barratry Abolition Act 1993. In Victoria, champerty and maintenance was abolished as a tort by section 32 of the Wrongs Act 1958, and as a crime by section 332A of the Crimes Act 1958.