New Hampshire and Maine share a border that runs from northwest to southeast. At the borders southeastern end, New Hampshires easternmost point meets Maines southernmost point. The boundary in this region follows the Piscataqua River eastward into Portsmouth Harbor and, from there, extends in a southeasterly direction into the sea. In 1977, in a dispute between the two States over lobster fishing rights, this Court entered a consent judgment setting the precise location of the States "lateral marine boundary," i.e., the boundary in the marine waters off the coast, from the closing line of Portsmouth Harbor five miles seaward. New Hampshire v. Maine, 426 U. S. 363; New Hampshire v. Maine, 434 U. S. 1, 2. The Piscataqua River boundary was fixed by a 1740 decree of King George II at the "Middle of the River." See 426 U. S., at 366-367. In the course of litigation, the two States proposed a consent decree in which they agreed, inter alia, that the descriptive words "Middle of the River" in the 1740 decree refer to the middle of the Piscataqua Rivers main navigable channel. Rejecting the Special Masters view that the quoted words mean the geographic middle of the river, this Court accepted the States interpretation and directed entry of the consent decree. Id., at 369-370. The final decree, entered in 1977, defined "Middle of the River" as "the middle of the main channel of navigation of the Piscataqua River." 434 U. S., at 2. The 1977 consent judgment fixed only the lateral marine boundary and not the inland Piscataqua River boundary. In 2000, New Hampshire brought this original action against Maine, claiming on the basis of historical records that the inland river boundary runs along the Maine shore and that the entire Piscataqua River and all of Portsmouth Harbor belong to New Hampshire. Maine has filed a motion to dismiss, urging that the earlier proceedings bar New Hampshires complaint.

Held: Judicial estoppel bars New Hampshire from asserting that the Piscataqua River boundary runs along the Maine shore. Pp. 5-13.

(a) Judicial estoppel is a doctrine distinct from the res judicata doctrines of claim and issue preclusion. Under the judicial estoppel doctrine, where a party assumes a certain position in a legal proceeding, and succeeds in maintaining that position, he may not thereafter, simply because his interests have changed, assume a contrary position, especially if it be to the prejudice of the party who has acquiesced in the position formerly taken by him. Davis v. Wakelee, 156 U. S. 680, 689. The purpose of the doctrine is to protect the integrity of the judicial process by prohibiting parties from deliberately changing positions according to the exigencies of the moment. Courts have recognized that the circumstances under which judicial estoppel may appropriately be invoked are not reducible to any general formulation. Nevertheless, several factors typically inform the decision whether to apply the doctrine in a particular case: First, a partys later position must be clearly inconsistent with its earlier position. Second, courts regularly inquire whether the party has succeeded in persuading a court to accept that partys earlier position, so that judicial acceptance of an inconsistent position in a later proceeding would create the perception that either the first or the second court was misled. Third, courts ask whether the party seeking to assert an inconsistent position would derive an unfair advantage or impose an unfair detriment on the opposing party if not estopped. In enumerating these factors, this Court does not establish inflexible prerequisites or an exhaustive formula for determining the applicability of judicial estoppel. Additional considerations may inform the doctrines application in specific factual contexts. Pp. 5-8.

(b) Considerations of eq