O’Melveny Worldwide

Anne T. Marchitello represents clients in a wide range of complex litigation matters, with particular experience in consumer class actions, product liability cases, and mass torts. She regularly advises companies on their most complex class action and product liability cases and has worked with these clients in state and federal courts across the country and at various stages of litigation, including pleadings, discovery, and trial.

A skilled litigator, Anne serves on trial teams defending major companies, including pharmaceutical and agricultural companies, against high-value claims. Anne’s experience ranges from detailed trial preparation work—including motions practice, fact development and discovery, and expert witness preparation—to key trial support. She has led large trial teams, managed extensive affirmative and defensive discovery, taken and defended depositions, and examined and cross-examined witnesses at trial.

Anne also devotes significant time to pro bono matters, including her successful representation of school districts and organizations in William Penn School District et al. v. Pennsylvania Department of Education et al., a landmark victory on behalf of Pennsylvania’s underfunded school districts and disadvantaged school children in which the Commonwealth Court declared that Pennsylvania’s school funding system is unconstitutional and must be reformed.

  • Represents an industry-leading pharmaceutical and consumer products company in federal multi-district litigation, coordinated state proceedings, and multi-plaintiff state proceedings relating to the marketing and sale of prescription opioid pain medications.
  • Represents a large company as national counsel in federal and state cases involving negligence, consumer protection, and other product liability claims.
  • Represented a major medical device company in several state and federal cases.
  • Prior to joining O’Melveny, represented a major agricultural company in federal multi-district litigation and state court proceedings.


Bar Admissions

  • District of Columbia
  • Maryland

Court Admissions

  • US Court of Appeals, Sixth Circuit
  • US District Court, District of Maryland


  • Georgetown University, J.D., 2015: Notes Editor, Georgetown Journal of Legal Ethics
  • Colgate University, B.A., 2010: magna cum laude

Professional Activities


  • US Attorney’s Office, District of Columbia
  • Domestic Violence Clinic, Georgetown University Law Center