The All India Trinamool Congress (AITC/TMC) was founded by Mamata Banerjee on January 1, 1998. Banerjee, who was a member of the Congress party for over 26 years, formed her own party in West Bengal and was allotted 'jora ghas phul' as exclusive symbol of the party. In the 1998 Lok Sabha elections, TMC won seven seats. In 1999, TMC bagged eight seats with BJP. In 2001 Legislative elections in West Bengal, TMC won 60 seats with the support of Congress and in 2006, it won 30 seats with BJP. In the 2009 Lok Sabha elections, TMC won 19 seats in Bengal.
TMC's 'Ma Mati Manush' slogan, which translates as 'Mother, Motherland and People' - coined by Mamata Banerjee, became very popular in West Bengal during 2011 Assembly elections. That year, people voted for political change by ending a 34-year-long rule of the Left regime. TMC and Congress alliance ushered this change.
In 2012, Mamata Banerjee decided to withdraw support to the UPA over diesel price hike and FDI in retail.
The 2016 Assembly election in West Bengal was historic as the Trinamool Congress was given a second chance with a massive mandate. TMC's victory in traditional left bastions made the Left Front almost insignificant in state politics. Other than populist and direct-benefit schemes, there also existed the hitherto unaddressed alternatives to the Left Front government way of functioning. That year, TMC independently secured 211 out of 294 seats.
TMC’s unprecedented popularity among the Scheduled Castes (SCs) and Scheduled Tribes (STs) led to its victory in almost all of the reserved constituencies. Direct cash benefits to the girl child through the Kanyashree Scheme, distribution of bicycles to all Class 10 and 11 students of virtually every school under the Sabooj Sathi scheme, and distribution of subsidised foodgrains to the poor under the National Food Security Act are some of the crucial direct measures that helped the TMC bag this landslide victory.
Since 2016, the party enjoys a National Party status after its expansion in Manipur, Odisha, Kerala, Sikkim, Arunachal Pradesh, Haryana, Assam and Tripura.
In the Lok Sabha elections 2014, the TMC had won 34 of the state's 42 seats, but in 2019 it suffered some setback, with the Bharatiya Janata Party (BJP) making inroads into West Bengal. Its seat tally came down to 22.