Heidi Beirich is a prominent American civil rights researcher, author, and activist specializing in the study and monitoring of extremist movements in the United States and Europe, with a focus on far-right networks, white supremacy, nativism, Islamophobia, anti-immigrant, antisemitic, and antigovernment groups targeting Muslims. She earned a Ph.D. in political science from Purdue University in 1998, with a dissertation on European fascism and neo-fascism, building on earlier degrees: a B.A. in International Development Studies from the University of California, Berkeley (1989), an M.A. in Economics from the University of California, Riverside (1990), and an M.A. in Political Science from San Diego State University (1993). Beirich has authored numerous academic publications on extremism and co-edited the book "Neo-Confederacy: A Critical Introduction" (University of Texas Press, 2008).

From around 1999/2000 to 2019, Beirich worked at the Southern Poverty Law Center (SPLC), where she held multiple leadership roles within its Intelligence Project, including Senior Writer, Deputy Director (2004–2009), Co-Director (2009–2012), and Director (2012–2019). In these roles, she oversaw the SPLC’s annual tracking of hate and antigovernment groups through reports such as "The Year in Hate and Extremism," "White Homicide Worldwide" (2014), and "The Nativist Lobby" (2009), as well as the Hate Map. She also developed policy positions on hate crimes and domestic terrorism, led campaigns to diminish the influence of hate organizations, and trained law enforcement on far-right threats. Beirich testified before Congress on white supremacy issues, including a 2020 appearance before the House Armed Services Committee concerning white supremacists in the military.

In 2019, amid internal controversies at SPLC regarding workplace culture, Beirich departed the organization and co-founded the Global Project Against Hate and Extremism (GPAHE), where she currently serves as Chief Strategy Officer. Through GPAHE and related initiatives such as the Change the Terms Coalition against online hate, she continues her work monitoring and countering global far-right extremism. She serves on the advisory board of the International Network for Hate Studies and is an advisor to the Christchurch Call Advisory Network. Beirich is a frequent speaker at conferences addressing hate, has been interviewed by major media outlets including The New York Times, The Washington Post, and the Los Angeles Times, and has appeared on television networks and documentaries focused on extremism.

Her work highlights connections between extremists and political, social, and religious institutions, exposes international far-right movements—including in Brazil and Europe—and advocates human rights–based resistance to extremism. She has investigated figures such as Richard Spencer and activists like Dan Stein, establishing adversarial relationships with some she critiques. Collaborating with scholars like Euan Hague and Edward H. Sebesta, Beirich has researched Confederate symbolism and neo-Confederate networks. While praised for rigorous documentation of hate groups, her work has also drawn criticism, along with the SPLC’s, from some conservatives who argue that designations of hate groups can be overly broad and may suppress free speech. Her research continues to influence policy debates and legislative discussions on domestic terrorism, including testimonies before lawmakers like Adam Smith and Bennie Thompson.