Thomas Sewell (born c. 1993) is a New Zealand–born Australian neo-Nazi activist and organiser, known for controversial public stunts, violent criminal conduct, and promotion of National Socialism. He is the leader of the National Socialist Network, the European Australian Movement and the founder of the Lads Society. The groups led by Sewell focus on promoting white supremacy and far-right activism in Australia.

According to Sewell, in 2017 he attempted to recruit Brenton Tarrant, the eventual perpetrator of the 2019 Christchurch mosque shootings, into the Lads Society. Sewell drew public condemnation in 2021 after he attacked a security guard at a television office. In October 2023, he was sentenced to a prison term of one month and seven days after attacking hikers at Victoria's Cathedral Range.

Sewell was born c. 1993 in New Zealand. He moved to Australia as a young child with his parents and older brother. He attended Balwyn High School in Melbourne, Australia, graduating in 2010. Between 2012 and 2014, he was an Australian Army infantryman. He then studied civil engineering at Swinburne University of Technology, but left without graduating. Sewell had a fiancée who was pregnant in January 2023.

Between 2015 and 2017 Sewell was a member of Reclaim Australia and the United Patriots Front (UPF). The UPF split from Reclaim Australia around May 2015. In the UPF, Sewell was the second in command of Blair Cottrell, the founder of the group. In late 2017, he and Cottrell founded the Lads Society, a now-defunct men's only far-right, white nationalist group that branded itself as a fitness group. Videos leaked to the press in November 2019 revealed Sewell's aim was to attract and recruit members from mainstream society using the pretense of a men's fitness club. According to Sewell, in 2017 he invited Brenton Tarrant (the perpetrator of the 2019 Christchurch mosque shootings) to join the Lads Society. Tarrant was then active in Facebook pages run by the Lads Society. Tarrant had praised the Lads Society's activism; Sewell later stated that Tarrant had refused to join as he did not see a peaceful solution to "European people being genocided".

Sewell founded the neo-Nazi National Socialist Network (NSN) in early 2021, and has since been its self-appointed leader. The NSN was established through a merger of the Lads Society and Antipodean Resistance. He is also the leader of the European Australian Movement (EAM), also established in 2021. In January 2021, over the Australia Day weekend, 38 members of EAM were photographed performing Nazi salutes next to Lake Bellfield at the foot of the Grampians in western Victoria. The group burnt a cross and chanted racist slogans at passers-by, including "White power" and Sieg Heil. The group's actions drew the attention of local police as well as intelligence officers from Victoria Police's Counter-Terrorism Command.

On 1 March 2021, the Australian TV program A Current Affair, a Nine Network program, broadcast a report on the NSN. An hour before it aired, Sewell and Jacob Hersant, a neo-Nazi associate of Sewell, arrived at Nine Network's Melbourne office demanding to speak to staff about the program. When a security guard, a black man, requested that they leave, Hersant said to the guard, "dance monkey, dance". The security guard was then repeatedly punched in the face and fell to the ground. Sewell continued to repeatedly hit the guard after he fell. When additional security came to the aid of the beaten man, Sewell and Hersant fled. The assault drew condemnation from Victorian Premier Daniel Andrews who called it "sickening". Victoria Police's Counter-Terrorism Command charged Sewell with affray, recklessly causing injury and unlawful assault. In December 2022, he contested the charges in the Melbourne Magistrates Court, attending with several supporters, including Blair Cottrell. Other supporters watched the proceedings online. The following week, Sewell was found guilty of affray and recklessly causing injury. On 12 January 2023, he was sentenced to an 18-month community corrections order with 150 hours of community service. After being sentenced, Sewell performed a Nazi salute outside the courtroom.

In May 2021, Sewell and up to 15 other masked men attacked hikers in Victoria's Cathedral Range. Sewell's blood was found inside the car of the attacked hikers. On 14 May 2021, Sewell was charged after a raid by counter-terrorism police at a house in the Melbourne suburb of Rowville. Sewell was charged with armed robbery, robbery, theft, criminal damage, affray with a face covering, affray, assault with a weapon, violent disorder, common law assault and committing an indictable offence while on bail. On 1 August 2023, Sewell and Jacob Hersant pleaded guilty to one charge of violent disorder. On 27 October 2023, Sewell was sentenced to one month and seven days in prison. As he had already served the sentence while on remand, he was spared further jail time.

In August 2021, Nick McKenzie hosted a segment on 60 Minutes showcasing their investigation involving an undercover operative infiltrating the NSN. In footage taken by the operative Sewell is heard stating that they were fighting for a white Australia and a global white revolution. During the segment Sewell is seen leading his members as they shout blood and honour, and perform Nazi salutes. At a later gathering Sewell and his members commemorate Adolf Hitler's birthday. McKenzie during the segment narrates that Sewell had a plan to build a white only base in rural Victoria, which Sewell states is their first goal. During part of the undercover footage, Sewell admits that during a previous police raid of his house that they found on his phone a meme celebrating Brenton Tarrant. Sewell goes on to state that he's opposed to Tarrant's jailing and that the NSN should fight for his release. Mike Burgess, chief of the Australian Security Intelligence Organisation (ASIO), stated that NSN views were of concern, especially when it came to promoting acts of violence, and that they were getting ASIO's as well as other law enforcement agencies' full attention.

On 18 March 2023, Sewell attended a rally in Melbourne with 30 other neo-Nazis, including members of the NSN. The rally was organised by British anti-trans activist Kellie-Jay Keen-Minshull and Moira Deeming, while Keen-Minshull was visiting the city on her Australian and New Zealand tour. Sewell and other members of the NSN marched down Spring Street, performed Nazi salutes on the stairs of Parliament House and referred to transgender people as paedophiles. The neo-Nazis clashed with others who were protesting in support of transgender rights. Police, including mounted officers, attempted to separate the groups. NSN's involvement in the rally was condemned by MPs from both the Labor Party, and the Liberal Party.

On Australia Day (26 January) 2024, Sewell and a group of NSN members were stopped and questioned by police in North Sydney. Sewell was served with a public order banning him from the city of Sydney local government area for the day, and from attending any events relating to Australia Day. Police told Sewell that the reasons for the order were his ideology, his associates, incidents he's been involved in, his criminal history and his goal of intimidating and provoking people.

On 22 October 2024 Sewell and other NSN members attempted to disrupt a refugee rights protest outside of a Department of Home Affairs office. Following the NSN's counterprotest Sewell allegedly made comments online in which he attempted to intimidate a police officer. In the alleged comments, Sewell stated that his followers had identified a Victoria police officer who had attempted to remove a mask from one of the neo-Nazis who had attended the counterprotest. Sewell said that the police officer had attempted to dox the member, and that they had downloaded content about the officer and their family from social media and were looking for a legal way to post it to the internet. In November 2024, Sewell was charged in relation to the alleged online comments after a police 'day of action' against the NSN.

Sewell is a neo-Nazi. He associates with other well-known neo-Nazis, including Neil Erikson who has also been a member of the UPF and the Lads Society.

Sewell is known for his violent promotion of National Socialism. The organisations that he leads promote white supremacy and far-right politics. They echo White genocide myths, claiming that white Australians are being "denigrated, attacked and replaced with foreigners". A leaked manual from Sewell's groups revealed how their members manipulate social media and journalists to gain publicity, amplify messaging and help them recruit new members. Sewell also appeals to "marginalized, underemployed young Australians in the fringes of society". In the leaked material Sewell has outlined plans to create "Anglo-European" enclaves in Australian cities. Sewell's stated goal was to encourage the "speed and ferocity of the decay" of society and to help foment a "race war" by exploiting issues raised by politicians. In August 2024, it was reported that Sewell was leading a cell of the Active Club in South Australia known as Croweater. Active Clubs attempt to attract young men under the guise of "training in sport or physical combat and fraternity". Sewell was suspended from X in July 2024, but the Croweater page remains, featuring a photo of masked members carrying a banner reading "Australia for the white man".

In an interview in 2019, Sewell was quoted as saying that he would see violence against minorities as an option "if the state continues its persecution of our people for wanting to preserve their culture and heritage". In a June 2024 podcast, Sewell falsely claimed that authorities in the United Kingdom had threatened to remove children from families because of their parent's political views. Sewell then said that he would commit acts of terrorism and encourage his followers to do likewise if the courts began ordering children to be removed from neo-Nazi parents. In the podcast, Sewell stated that "[w]e want a white Australia for our children so they have a home to live in in the future". When asked by ABC News if recommending violence was acceptable, he stated that "terrorising white Australians for their political beliefs" would result in an "irreversible chain of events". Kristy Campion, who studies Australian far-right extremism, stated that central to the NSN's worldview "is the belief that if they do not act, it will be their children who suffer". She stated that far-right terrorists have repeatedly justified violent acts on the basis of their children.