Greenwald was born on March 6, 1967, in New York City, where he still lives part of the year. He earned a B.A. from George Washington University in 1990 and a J.D. from New York University Law School in 1994. During law school, he worked as an intern and Summer Associate at the New York law firm of Wachtell, Lipton, Rosen & Katz, and after graduation, he practiced law in the Litigation Department at Wachtell, Lipton (1994—1995); in 1996 he co-founded his own litigation firm, called Greenwald Christoph & Holland (later renamed Greenwald Christoph PC), where he litigated cases concerning issues of U.S. constitutional law and civil rights.

One of Greenwald's most notable First Amendment clients was Matthew Hale, a leader of the organization formerly known as the World Church of the Creator and now known as the Creativity Movement, who, on April 6, 2005, was sentenced to a 40-year prison term for soliciting an undercover FBI informant to kill federal judge Joan Lefkow and incarcerated in the United States Penitentiary Administrative Maximum Facility in Florence, Colorado. Although he "represented Hale and his organization in several civil cases" and was not involved in Hale's criminal defense case, after the subsequent killing of Judge Lefkow's mother and husband while Hale was incarcerated for the earlier conviction, Greenwald was enlisted by Hale's mother, Evelyn Hutcheson, to deliver a purportedly "encoded message" from the imprisoned Hale to one of his supporters on the outside; but, despite believing that Hale had been wrongfully convicted and uninvolved in the more recent murders, Greenwald declined to do so.

In his entry in Unclaimed Territory for July 10, 2006, Greenwald explains, "I decided voluntarily to wind down my practice in 2005 because I could, and because, after ten years, I was bored with litigating full-time and wanted to do other things which I thought were more engaging and could make more of an impact, including political writing."

In the same entry, Greenwald observes that he has been openly gay for 20 years and that, while he has lived in the United States all his life, he divides his time between New York City and Rio de Janeiro, the hometown of his male partner:

Revealingly, American law prevents the recognition of our relationship as a ground for him to live in the United States, while Brazilian law recognizes same-sex relationships for visa and immigration purposes. As a result, for the past year [2006], I have spent substantial time in Brazil while also having a residence in New York. Spending substantial time in another country does not make one an 'expatriate.' And even those American citizens who do give up American residence and live abroad retain full rights of citizenship, including voting rights. But I have not done so.

According to Ken Silverstein's interview with Greenwald published in Harper's Magazine on February 22, 2008, conducted by telephone while Greenwald was in Brazil, he lives there "much of the time." On July 22, 2008, when Greenwald participated in a debate with Cass Sunstein, an adviser to then Senator Barack Obama, moderated by Amy Goodman on Democracy Now!, their exchange was also conducted by telephone from Brazil.

In a May, 2008 interview, Greenwald explained that "even though Brazil has the largest Catholic population of any country in the world" and "was a military dictatorship until 1985": "I’m able to obtain from the Brazilian government a permanent visa because my Brazilian partner’s government recognizes our relationship for immigration purposes, while the government of my supposedly 'free,' liberty-loving country enacted a law explicitly barring such recognition."

The New York Times describes Greenwald as a liberal.

In the preface to his first book, How Would a Patriot Act? (2006), Greenwald begins by giving some of his own personal political history, describing himself as at first neither liberal nor conservative but as one who had taken positions that can be ascribed to both liberals and conservatives, voting neither for George W. Bush nor for any of his rivals, indeed not voting at all.

Bush's ascendancy to the U.S. Presidency "changed" Greenwald's previous uninvolved political attitude toward the electoral process "completely":

Over the past five years, a creeping extremism has taken hold of our federal government, and it is threatening to radically alter our system of government and who we are as a nation. This extremism is neither conservative nor liberal in nature, but is instead driven by theories of unlimited presidential power that are wholly alien, and antithetical, to the core political values that have governed this country since its founding"; for, "the fact that this seizure of ever-expanding presidential power is largely justified through endless, rank fear-mongering...fear of terrorists, specifically...means that not only our system of government is radically changing, but so, too, are our national character, our national identity, and what it means to be American."

Believing that "It is incumbent upon all Americans who believe in that system, bequeathed to us by the founders, to defend it when it is under assault and in jeopardy. And today it is," he stresses: "I did not arrive at these conclusions eagerly or because I was predisposed by any previous partisan viewpoint. Quite the contrary."

Ostensibly resistant to applying ideological labels to himself, he emphasizes repeatedly that he is a strong advocate for U.S. constitutional "balance of powers" and for constitutionally-protected civil and political rights in his writings and public appearances.

Throughout them he has relentlessly criticized the policies of the George W. Bush administration and those who support or enable it, arguing that most of the American "Corporate News Media" excuse Bush's policies and echo administration talking points rather than asking hard questions.

Entitling his Unclaimed Territory blog entry for January 16, 2006, "Bush Followers Are Not Conservatives," Greenwald explains this position:

It has long been clear that there is nothing remotely "conservative" about this Administration, at least in the sense that conservative ideology has stood for a restrained Federal Government which was to be distrusted. There has been a long line of decidedly un-conservative actions by this Administration -- from exploding discretionary domestic spending to record deficits to an emergency convening of the Federal Government to intervene in one woman’s end-of-life decisions to attempts to federalize, even constitutionalize, marriage laws — all of which could not be any more alien to what has been meant by "conservatism" for the past 40 years.

In his various media guest appearances and publications, Greenwald elaborates his political views, which he also summarizes succinctly in responding to "six questions ... about political campaign coverage and the media" that Ken Silverstein posed to him in an article published in Harper's Magazine on February 21, 2008.

Greenwald holds a favourable view of drug liberalization. He conducted research, commissioned by the Cato Institute, on the effect of the abolition of all criminal penalties for personal drug possession in Portugal, which occurred in 2001. According to Greenwald, "decriminalization in Portugal has been a resounding success... It has enabled the Portuguese government to manage and control the drug problem far better than virtually every other Western country does".

Greenwald started his blog Unclaimed Territory in October 2005, focusing initially on the investigation pertaining to the Plame affair, the CIA leak grand jury investigation, and the federal indictment of I. Lewis "Scooter" Libby. Two months later, when the National Security Agency warrantless surveillance controversy became news, he began to focus primarily on that issue. In January 2006 Greenwald attracted national media attention after he wrote in Unclaimed Territory that U.S. Senator Mike DeWine had proposed an easier standard for domestic eavesdropping by federal agents in 2002 but that the administration had declined any interest in the legislation and advised him that it would probably be unconstitutional, a direct contradiction of much of the later rationale for the NSA warrantless domestic spying program once it was known; Dan Eggen, of The Washington Post, for example, observed that "The DeWine amendment" ... "the latest point of contention in a fierce political and legal battle over the NSA monitoring program" ... was "first highlighted ... by Internet blogger Glenn Greenwald and widely publicized yesterday by the Project on Government Secrecy, an arm of the Federation of American Scientists...."

In March 2006, Senator Russ Feingold quoted Greenwald's comments in Unclaimed Territory on the floor of the U.S. Senate when he introduced Senate Resolution 398, to censure President Bush.

In April 2006, Unclaimed Territory received the 2005 Koufax Award for "Best New Blog".

In February 2008, during a debate over the FISA and Telecom Immunity bill on the floor of the U.S. Senate broadcast on C-Span, Senator Chris Dodd quoted Greenwald's comments posted in Unclaimed Territory.

In February 2007, Greenwald became a contributing writer at Salon.com, and the new column and blog superseded Unclaimed Territory, though Salon.com prominently features hyperlinks to it in Greenwald's dedicated biographical section.

Joe Klein

In his Salon.com column of November 21, 2007, Greenwald documented factual errors in a national column written by Joe Klein in Time magazine. In response to such criticism, Time subsequently added an intended clarification (or quasi-retraction) in an online version of Klein's disputed column ... "In the original version of this story, Joe Klein wrote that the House Democratic version of the Foreign Intelligence Surveillance Act would allow a court review of individual foreign surveillance targets. Republicans believe the bill can be interpreted that way, but Democrats don't." ... but Greenwald observed that the text of the legislation does not require court review of individual targets, and Time 's response repeating "what each side says" disregards that point. Pertaining to this controversy, Time published letters from U.S. Senator Russ Feingold and others in its later issues of the magazine.

Anthrax reporting

In August 2008, following the suicide of terrorist suspect Bruce Ivins, Greenwald wrote a series of long entries, detailing the evidence that there has been a cover-up by individuals in the US government and ABC News in the 2001 anthrax attacks, calling for "a full-scale Congressional hearing or even an external Commission of the type that investigated the 9/11 attacks - endowed with full subpoena power - to examine all of the unresolved issues here." Greenwald also expressed interest in the identity of the individual who allegedly told ABC News' Brian Ross falsely in 2001 that the anthrax contained bentonite and falsely linking the anthrax attack to Saddam Hussein and argued that the broadcasting of this claim by ABC News was instrumental in guiding the US media and public opinion towards war with Iraq; subsequently, according to Dan Gillmor, who prominently cites and links to Greenwald in an article published in the Guardian.co.uk, Brian Ross refused to divulge the identity of the individual who purportedly misled him.

John O. Brennan

After U.S. President-elect Barack Obama's victory in November 2008, the media reported that former CIA official John O. Brennan, who had served as Senator Obama's top intelligence adviser during his 2008 election campaign, was the leading candidate to be named by Obama as either the next Director of the Central Intelligence Agency (D/CIA) or the next Director of National Intelligence (DNI). In a lengthy essay published in Salon.com, Greenwald argued that Brennan had supported many controversial detention and interrogation policies of the Bush administration, including "enhanced interrogation tactics" and extraordinary rendition. Other notable writers such as Andrew Sullivan credited Greenwald's Salon.com essay as the impetus for their opposition to Brennan's nomination. On November 24, Brennan wrote a letter to President-elect Obama withdrawing his name from consideration for any top intelligence posts, citing "strong criticism in some quarters." Media reports and other political pundits cited the "firestorm in liberal blogs" as the cause of Brennan's withdrawal.

Greenwald's first book, How Would a Patriot Act? Defending American Values From a President Run Amok, published by Working Assets, in 2006, was a New York Times bestseller and ranked number one on Amazon.com both before its publication due to pre-orders based on attention from other bloggers and for several days after its release, ending its first week at number 293.

A Tragic Legacy, his second book, aims to examine the presidency of George W. Bush "with an emphasis on his personality traits and beliefs that drove the presidency (along with an emphasis on how and why those personality traits have led to a presidency that has failed to historic proportions)." Published in hardback by Crown, a division of Random House, on June 26, 2007, and later reprinted in a paperback edition by Three Rivers Press on April 8, 2008, it also appeared on "The New York Times Best Seller List" after its original release and was ranked number one for a day on Amazon.com's "Non-Fiction Best Seller List", before becoming number two the next day, also due to heavy "discussions and promotions by blogs -- a campaign catalyzed by Jane Hamsher [at FireDogLake]," according to Greenwald.

His third book, entitled Great American Hypocrites, was published by Random House in April 2008, the same month that Three Rivers Press reissued A Tragic Legacy in paperback.

Greenwald has appeared as a roundtable guest on ABC's Sunday morning news show "This Week," NPR's "All Things Considered," as well as numerous times on C-SPAN's Washington Journal; Pacifica Radio's syndicated series Democracy Now! with Amy Goodman; on Public Radio International's To the Point; MSNBC's The Rachel Maddow Show, "Morning Joe" and Dylan Ratigan's "Morning Meeting"; and on Fox News' Special Report with Brit Hume. Greenwald has also become a regular guest on PBS's Bill Moyers Journal., and is a regular guest on the Hugh Hewitt Show, and was a friend and favorite guest of Hewitt's frequent guest host, Dean Barnett.

On August 24, 2008, the day before the start of the 2008 Democratic National Convention, which was held in Denver, Colorado, Dan Amira of New York magazine ranked Greenwald as number 36 in his list of "top 40" most popular American political pundit.

On January 22, 2009, Forbes named Greenwald one of the "25 Most Influential Liberals in the U.S. Media". The magazine placed him at number eighteen, just below Hendrik Hertzberg and just ahead of Andrew Sullivan.

On July 6, 2009, former MSNBC host Dan Abrams launched a new site, Mediaite, reporting on media figures. The site ranked all print and online columnists in America by influence. Greenwald was ranked # 9, immediately behind Charles Krauthammer.

In August 2009, the Web search engine Technorati ranked Glenn Greenwald's Salon.com blog as number 45 in its "Top 100" list of "the most popular 100 blogs based on Technorati Authority" (in its case, 2,056 blog links in the past six months).

In November, 2009, The Atlantic launched a new site, [TheAtlanticWire.com], and named America's 50 most influential political pundits ("The Atlantic 50"). Greenwald was ranked #22 on the list.

Greenwald, Glenn. Toppling the Big Myths of Republican Politics. New York: Random House, 2008. ISBN 0-307-40802-7 (10). ISBN 978-0-307-40802-0 (13). (Also available as an E-book.)

———. How Would a Patriot Act? Defending American Values From A President Run Amok. San Francisco: Working Assets (Distrib. by Publishers Group West), 2006. ISBN 0-9779440-0-X (10). ISBN 978-0-9779440-0-2 (13).

———. How a Good vs. Evil Mentality Destroyed the Bush Presidency. New York: Crown (Div. of Random House), 2007. ISBN 0-307-35419-9 (10). ISBN 978-0-307-35419-8 (13). (Hardback ed.) Three Rivers Press, 2008. ISBN 0-307-35428-8 (10). ISBN 978-0-307-35428-0 (13). (Paperback ed.)

Video interviews

• Greenwald on Afghanistan, State Secrets, Healthcare and the Media - by Democracy Now!
• Greenwald on Iran, Tea Party Candidates, Jon Stewart and Obama’s Assassination Policy - by Democracy Now!

Glenn Greenwald