The state pension accounts for £6 in every £10 of retirement income received by British adults aged 65 and over on average, research by Just Group has revealed.
Nearly three-quarters of this age group receive at least half of their income from the state pension, according to the research, with women and poorer people most reliant.
Only those with an annual retirement income of over £20,000 receive more from defined benefit (DB) pensions than they do from the state.
This comes in the same month that the state pension age begins to rise for both men and women, reaching 66 by October 2020 before a further planned increase to 67 in 2026.
Just Group said the findings highlight how the state pension is the "financial bedrock" for later life, warning that its significance "should not be underestimated".
Communications director, Stephen Lowe, said: "The rise in the state pension to 66 is now underway, coupled with the planned rise to 67, these change are likely to have a major effect on the labour market.
"We can expect to see the growth in the number of older workers make up a large part of the rise in overall employment for the next decade."
The research shows that over-65s on annual retirement income of less than £5,000 receive around 90% from the state pension, while women of this age get 68% from the state.
However, it was also found that just 15% of those aged 65 and over can retire completely living off the state pension, with 57% also relying on separate pensions and savings.
This comes after the UK's state pension was ranked worst in the OECD, with British pensioners receiving a lower percentage of their working salary than any other country.
The OECD found that 18.5% of people aged over 75 in the UK live in poverty, compared with 11% among the country's whole population, with women worst affected.
"People who have had sufficient income during their working lives to save and contribute to private pensions have relatively good incomes," the OECD said.
"However, retirees without such additional sources of revenue are left with few resources - this is reflected in the poverty rate and high income inequality in the UK."