António José Martins Seguro (Penamacor, 11 de março de 1962) é um político português, membro do Partido Socialista. Estudou Gestão de Empresas, no Instituto Superior de Ciências do Trabalho e da Empresa, mas acabou por se licenciar em Relações Internacionais, na Universidade Autónoma de Lisboa.
Foi director do jornal A Verdade ou Mentira, e chegou a secretário-geral da Juventude Socialista, cargo que ocupou entre 1990 e 1994. Deputado à Assembleia da República, de 1991 a 1995, veio a integrar os XIII e XIV Governos Constitucionais, tendo ocupado o seu último cargo governativo como ministro-adjunto de António Guterres, entre 2001 e 2002. Entre 1999 e 2001 foi deputado ao Parlamento Europeu, tendo sido co-autor do Relatório do Parlamento Europeu sobre o Tratado de Nice e o futuro da União Europeia.
Em 2002 regressou à Assembleia da República, onde liderou a bancada parlamentar do PS (VIII Legislatura), presidiu à Comissão Parlamentar de Educação e Ciência (X Legislatura) e é hoje presidente da Comissão de Assuntos Económicos, Inovação e Energia (XI Legislatura). Dirigiu também o Gabinete de Estudos Nacional do PS, de 2002 até 2004. Foi eleito secretário-geral do Partido Socialista a 24 de Julho de 2011 com 23 943 votos (67,98%), contra os 11 280 (32,02%) votos do concorrente, Francisco Assis.
António José Martins Seguro (born 11 March 1962) is a Portuguese politician for the Socialist Party (PS). Seguro has been Secretary General of the PS since 2011, and he is the main leader of the opposition in the Portuguese Parliament.
Seguro became involved in political activities from a very young age, always linked to the Socialist Party (PS). He was successively secretary general of Socialist Youth, president of the National Youth Council and chairman of the Youth Forum of the European Communities. He was first elected to the Portuguese Parliament in 1991, and again eight years later. In 1995, the Socialist Party won the parliamentary elections, leaving the leader António Guterres to form a government.
Seguro initially was Secretary of State for Youth and later assistant secretary of State's prime minister. After a cabinet reshuffle he was promoted to Deputy Minister of the Prime Minister. He also played the role of coordinator of the Standing Committee of the Portuguese Socialist Party and president of the Municipal Assembly of Penamacor. In 1999, António Guterres's PS again won the legislative elections and formed the XIV Constitutional Government, but Seguro moved to other functions. The former cabinet member was elected deputy to the European Parliament, between July 1999 and July 2001. In these two years, serving in the parliament, he was an effective member of the Committee on Constitutional Affairs (in these functions he was co-author of the Report on the Treaty of Nice and the Future of the European Union) and a substitute for the Commission for Employment and Social Affairs. He was also president of the Delegation for Relations with Central America and Mexico, vice president of the Socialist Group in the European Parliament and president of the Portuguese Socialist delegation. After leaving Parliament, he returned to the parliament, being reelected in the elections of 2002. He was also appointed member of the National Secretariat of the Socialist Party. After the municipal elections of December 2002, he accumulated these positions with membership in the Municipal Assembly of Gouveia.
After Prime Minister José Sócrates resigned as PS General Secretary on the election night of 5 June 2011, having lost the general election by a margin higher than expected, Seguro was elected leader of the party on 23 July 2011, winning 68%
of the vote; his challenger, Francisco Assis, got 32%. In 2013, he was listed as one of the attendees of the annual Bilderberg Group conference with the title 'Secretary General, Socialist Party'.