It is not unreasonable to assume that, in generally requiring complete diversity, Congress did not intend to confine the jurisdiction of federal courts so inflexibly that they are unable to protect legal rights or effectively to resolve an entire, logically entwined lawsuit. Those practical needs are the basis of the doctrine of ancillary jurisdiction. But neither the convenience of litigants nor considerations of judicial economy can suffice to justify extension of the doctrine of ancillary jurisdiction to a plaintiff's cause of action against a citizen of the same State in a diversity case. Congress has established the basic rule that diversity jurisdiction exists under 28 U. S. C. § 1332 only when there is complete diversity of citizenship. "The policy of the statute calls for its strict construction." Healy v. Ratta, 292 U. S. 263, 270; Indianapolis v. Chase Nat. Bank, 314 U. S. 63, 76; Thomson v. Gaskill, 315 U. S. 442, 446; Snyder v. Harris, 394 U. S., at 340. To allow the requirement of complete diversity to be circumvented as it was in this case would simply flout the congressional command.2

Accordingly, the judgment of the Court of Appeals is reversed.

It is so ordered.

MR. JUSTICE WHITE, with whom MR. JUSTICE BRENNAN joins, dissenting.

The Court today states that "[i]t is not unreasonable to assume that, in generally requiring complete diversity, Congress did not intend to confine the jurisdiction of federal courts so

law. See Iowa Code § 614.10 (1977). Compare 558 F. 2d, at 420, with id., at 432 n. 42 (Bright, J., dissenting); cf. Burnett v. New York Central R. Co., 380 U. S. 424, 431-432, and n. 9.

21 Our holding is that the District Court lacked power to entertain the respondent's lawsuit against the petitioner. Thus, the asserted inequity in the respondent's alleged concealment of its citizenship is irrelevant. Federal judicial power does not depend upon "prior action or consent of the parties." American Fire & Cas. Co. v. Finn, 341 U. S., at 17-18.

inflexibly that they are unable . . . effectively to resolve an entire, logically entwined lawsuit." Ante, at 377. In spite of this recognition, the majority goes on to hold that in diversity suits federal courts do not have the jurisdictional power to entertain a claim asserted by a plaintiff against a third-party defendant, no matter how entwined it is with the matter already before the court, unless there is an independent basis for jurisdiction over that claim. Because I find no support for such a requirement in either Art. III of the Constitution or in any statutory law, I dissent from the Court's "unnecessarily grudging" approach.

The plaintiff below, Mrs. Kroger, chose to bring her lawsuit against the Omaha Public Power District (OPPD) in Federal District Court. No one questions the power of the District Court to entertain this claim, for Mrs. Kroger at the time was a citizen of Iowa, OPPD was a citizen of Nebraska, and the amount in controversy was greater than $10,000; jurisdiction therefore existed under 28 U. S. C. § 1332 (a). As permitted by Fed. Rule Civ. Proc. 14 (a), OPPD impleaded petitioner Owen Equipment & Erection Co. (Owen). Although OPPD's claim against Owen did not raise a federal question and although it was alleged that Owen was a citizen of the same State as OPPD, the parties and the court apparently believed that the District Court's ancillary jurisdiction encompassed this claim. Subsequently, Mrs. Kroger asserted a claim against Owen, everyone believing at the time that these two parties were citizens of different States. Because it later came to light that Mrs. Kroger and Owen were in fact both citizens of Iowa, the Court concludes that the District Court lacked jurisdiction over the claim.

In Mine Workers v. Gibbs, 383 U. S. 715, 725 (1966), we held that once a claim has been stated that is of sufficient substance to confer subject-matter jurisdiction on the federal dis

1 See Mine Workers v. Gibbs, 383 U. S. 715, 725 (1966).

trict court, the court has judicial power to consider a nonfederal claim if it and the federal claim 2 are derived from "a common nucleus of operative fact." Although the specific facts of that case concerned a state claim that was said to be pendent to a federal-question claim, the Court's language and reasoning were broad enough to cover the instant factual situation: "[I]f, considered without regard to their federal or state character, a plaintiff's claims are such that he would ordinarily be expected to try them all in one judicial proceeding, then, assuming substantiality of the federal issues, there is power in federal courts to hear the whole." Ibid. (footnote omitted). In the present case, Mrs. Kroger's claim against Owen and her claim against OPPD derived from a common nucleus of fact; this is necessarily so because in order for a plaintiff to assert a claim against a third-party defendant, Fed. Rule Civ. Proc. 14 (a) requires that it "aris [e] out of the transaction or occurrence that is the subject matter of the plaintiff's claim against the third-party plaintiff...." Furthermore, the substantiality of the claim Mrs. Kroger asserted against OPPD is unquestioned. Accordingly, as far as Art. III of the Constitution is concerned, the District Court had power to entertain Mrs. Kroger's claim against Owen.

The majority correctly points out, however, that the analysis cannot stop here. As Aldinger v. Howard, 427 U. S. 1 (1976), teaches, the jurisdictional power of the federal courts may be limited by Congress, as well as by the Constitution. In Aldinger, although the plaintiff's state claim against Spokane County was closely connected with her 42 U. S. C. § 1983 claim against the county treasurer, the Court held that the District Court did not have pendent jurisdiction over the state claim, for, under the Court's precedents at that time, it was thought that Congress had specifically determined not to confer on the federal courts jurisdiction over civil rights

2 I use the terms "federal claim" and "nonfederal claim" in the same sense that the majority uses them. See ante, at 372 n. 11.

claims against cities and counties. That being so, the Court refused to allow "the federal courts to fashion a jurisdictional doctrine under the general language of Art. III enabling them to circumvent this exclusion . . . .” 427 U. S., at 16.'

In the present case, the only indication of congressional intent that the Court can find is that contained in the diversity jurisdictional statute, 28 U. S. C. § 1332 (a), which states that "district courts shall have original jurisdiction of all civil actions where the matter in controversy exceeds the sum or value of $10,000... and is between ... citizens of different States... Because this statute has been interpreted as requiring complete diversity of citizenship between each plaintiff and each defendant, Strawbridge v. Curtiss, 3 Cranch 267 (1806), the Court holds that the District Court did not have ancillary jurisdiction over Mrs. Kroger's claim against Owen. In so holding, the Court unnecessarily expands the scope of the complete-diversity requirement while substantially limiting the doctrine of ancillary jurisdiction.

The complete-diversity requirement, of course, could be viewed as meaning that in a diversity case, a federal district court may adjudicate only those claims that are between parties of different States. Thus, in order for a defendant to implead a third-party defendant, there would have to be diversity of citizenship; the same would also be true for crossclaims between defendants and for a third-party defendant's claim against a plaintiff. Even the majority, however, refuses to read the complete-diversity requirement so broadly; it

We were careful in Aldinger to point out the limited nature of our holding:

"There are, of course, many variations in the language which Congress has employed to confer jurisdiction upon the federal courts, and we decide here only the issue of so-called 'pendent party' jurisdiction with respect to a claim brought under §§ 1343 (3) and 1983. Other statutory grants and other alignments of parties and claims might call for a different result." 427 U. S., at 18.

recognizes with seeming approval the exercise of ancillary jurisdiction over nonfederal claims in situations involving impleader, cross-claims, and counterclaims. See ante, at 375. Given the Court's willingness to recognize ancillary jurisdiction in these contexts, despite the requirements of § 1332 (a), I see no justification for the Court's refusal to approve the District Court's exercise of ancillary jurisdiction in the present

case.

It is significant that a plaintiff who asserts a claim against a third-party defendant is not seeking to add a new party to the lawsuit. In the present case, for example, Owen had already been brought into the suit by OPPD, and, that having been done, Mrs. Kroger merely sought to assert against Owen a claim arising out of the same transaction that was already before the court. Thus the situation presented here is unlike that in Aldinger, supra, wherein the Court noted:

"[I]t is one thing to authorize two parties, already present in federal court by virtue of a case over which the court has jurisdiction, to litigate in addition to their federal claim a state-law claim over which there is no independent basis of federal jurisdiction. But it is quite another thing to permit a plaintiff, who has asserted a claim against one defendant with respect to which there is federal jurisdiction, to join an entirely different defendant on the basis of a state-law claim over which there is no independent basis of federal jurisdiction, simply because his claim against the first defendant and his claim against the second defendant 'derive from a common nucleus of operative fact.' . . . True, the same considerations of judicial economy would be served insofar as plaintiff's claims 'are such that he would ordinarily be expected to try them all in one judicial proceeding.... [Gibbs, 383 U. S., at 725.] But the addition of a completely new party would run counter to the well-established principle that federal courts, as opposed to state trial courts of