In 2001, six female employees of Walmart filed suit against their company in US federal court alleging that Walmart discriminated against them in salary, bonuses and training.  After extensive discovery and oral argument, in 2003 the plaintiffs filed an amended complaint requesting that the court certify the case as a class action on behalf of current and former female Walmart employees maintaining that the discrimination faced by the original plaintiffs was systematic in nature and affected all women employed by Walmart.  In June of 2004, the court granted the plaintiffs’ motion for class certification. The lawsuit represents approximately 1.5 million current and former female Walmart employees, which makes it the largest workplace bias case in US history.  Walmart appealed the class certification decision. 

In February of 2007, the Ninth Circuit Court of Appeals upheld the lower court's ruling granting class action status to this gender discrimination lawsuit.  In February 2009, the Ninth Circuit Court of Appeals granted Walmart's request for an en banc review of the lower court's ruling granting class action status.  This review was heard in late March 2009.  In April 2010, the Ninth Circuit Court of Appeals ruled that this lawsuit could move forward to trial as a class action lawsuit.  Walmart petitioned the Supreme Court in August 2010 asking it to hear an appeal of the Ninth Circuit Court's ruling allowing this lawsuit to proceed as a class action.  The company maintains that the claims should be handled individually (or in smaller groups) rather than as a class of more than one million women.  In December 2010 the Supreme Court announced that it would hear Walmart's appeal in this case.  The Court heard oral arguments in late March 2011.  The Court issued its ruling on 20 June 2011 reversing the court of appeals decision, and ruling that the class could not go forward.

On 27 October 2011, the plaintiffs re-filed their complaint with the federal court in San Francisco, claiming gender bias on behalf of workers in California.  On 16 January 2012, the defendants filed a motion to dismiss the suit, claiming the smaller proposed class action seeks to cover all women who were employed at any Walmart in any region that included a California store.  This motion to dismiss was rejected by the court of appeals in September 2012.  In August 2013, however, the district court issued an order denying the women class certification.  If the women want to pursue the claims against Walmart, they will have to each pursue their respective claims individually.

In June 2012, nearly 2,000 female Walmart employees filed discrimination charges against the company with the U.S. Equal Employment Opportunity Commission.

In November 2017, seven women who were part of the 2001 suit filed a new lawsuit in Florida Southern District Court alleging gender discrimination in compensation and promotion against Walmart and Sam’s Club female employees in three regions in the southeastern USA. The plaintiffs are asking for compensation including back pay and damages for lost compensation and job benefits. Walmart once again declared that these claims were not suited to qualify as class action.

In 2018, the Supreme Court ruled in an unrelated case that, after a class action is dismissed, further actions have to be brought individually, not as smaller classes, to be considered timely. The plaintiffs remain resolute, claiming that the courts did not yet ruled on the actual claims but only on procedural matters.

In 2019, Walmart faced another wave of gender discrimination lawsuits filed by nearly 100 current and former female employees, alleging unequal pay and lack of opportunity.

• "Walmart facing gender discrimination lawsuits from female employees", Michael Sainato, The Guardian, 18 Feb 2019
• "Wal-Mart Female Employees Try Again for Sex-Bias Class Action", Jordyn Holman, Bloomberg 7 Nov 2017
• "Judge sinks class in Wal-Mart gender bias suit", Anne Youderian, Courthouse News Service, 5 Aug 2013
• "Wal-Mart must face California bias case, Judge Rules", Karen Gullo & Joel Rosenblatt, Bloomberg News 22 Sep 2012
• “2,000 Women File Wal-Mart Gender Discrimination Charges with EEOC”, Matt O'Donnell, Top Class Actions, 16 Jun 2012
• "Mart seeks end to refiled gender-bias lawsuit", Dan Levine, Reuters, 17 Jan 2012
• "Wal-Mart Workers Limit Gender Bias Suit to California Stores", Margaret Cronin Fisk, Karen Gullo, 27 Oct 2011
• "Supreme Court sides with Wal-Mart in sex discrimination lawsuit", Bloomberg, 20 Jun 2011
• "Wal-Mart Gets High Court Review in Million-Worker Bias Case", Greg Stohr, Bloomberg, 6 Dec 2010
• "Wal-Mart Asks Supreme Court To Hear Bias Suit", Steven Greenhouse, New York Times, 25 Aug 2010
• “Walmart fails to halt suit”, Bloomberg News, 12 Dec 2007
• "Wal-Mart Loses Bid to Block Group Suit in Bias Case", Karen Gullo & Margaret Cronin Fisk, Bloomberg News, 6 Feb 2007 
• “Wal-Mart Asks Court To Narrow Bias Lawsuit”, Bloomberg News, 9 Aug 2005
• “Wal-Mart Wants to Declassify Lawsuit”, Anthony Sebok, FindLaw, 11 Aug 2004
• “Wal-Mart Bias Case Moves Forward”, Amy Joyce, Washington Post, 23 Jun 2004
• Wal-Mart: Wal-Mart Will Seek Further Appellate Review In Gender Class Action Lawsuit, 6 Feb 2007 
• Wal-Mart: [PDF] Employment and Diversity Factsheet, 24 Jan 2007
• Website for plaintiffs and information for members and potential members of the class action lawsuit: Wal-Mart Class Website
• Equal Rights Advocates (co-counsel for plaintiffs): Dukes v. Wal-Mart Stores (includes summary of the case and links to certain legal documents) 
• US District Court for the Northern District of California: [PDF]Dukes, et al. v. Wal-Mart Stores, Inc. - Order Denying Class Certification, 2 Aug 2013
• US Supreme Court: [PDF] Wal-Mart Stores, Inc. v. Dukes et al. - Opinion of the Court, 20 Jun 2011
• [PDF] Wal-Mart Stores, Inc. v. Dukes et al. - Petition for a Writ of Certiorari, 25 Aug 2010 [Wal-Mart's petition to the Supreme Court asking it to hear an appeal of the Ninth Circuit's decision]
• US Court of Appeals for the Ninth Circuit: [PDF] Dukes v. Wal-Mart Inc., 26 Apr 2010
• US Court of Appeals for the Ninth Circuit: [PDF] Dukes v. Wal-Mart Inc., 11 Dec 2007
• US Court of Appeals for the Ninth Circuit: [PDF] Dukes v. Wal-Mart, Inc., 6 Feb 2007