Twitter was awash with dedications of thanks to the healthcare provider, including messages from Sarah Brown, Caitlin Moran and comedian Marcus Brigstocke.
HuffPost UK has collated some of the messages below - including gratitude for “stitching up fingers”, “saving lives” and “injecting my bum with a tetanus shot” - but let us know in the comments what you would like to thank the NHS for.
The prime minister hailed the NHS as a "wonderful institution", saying that "there is a lot to celebrate" about the insitition whilst acknowledging the "pressures and problems" it faces.
David Cameron said: "Of course there are pressures and problems but there is a lot to celebrate - mixed-sex wards that bugged the NHS for years are almost abolished, rates of infections in our hospitals are at an all-time low, record numbers of patients being treated, and the NHS is doing things in terms of new treatments that were unheard-of and undreamt-of years ago.
"So yes, let's shine a light on the problem areas and, yes, let's always be on the side of the patient ,but there is a lot to celebrate about this wonderful institution, as I know from my own family history. My son was treated right here in this fabulous hospital for much of his life."
The health secretary also praised the work of the NHS and at an event celebrating its birthday, Jeremy Mr Hunt said: "The NHS is the nation's most loved and most successful institution.
"In 65 years, the NHS has quite simply done more to improve people's lives that any other institution in our history, and its equity and excellence make us the envy of the world. Today we express our thanks to the millions of hard-working NHS staff who literally save lives round the clock. We owe them a huge debt of gratitude.
"But as we celebrate, we also reflect. The world today is very different to 1948. The old model was curable illnesses where you went into hospital unwell and came out better.
"Yet most people now leave hospital with long-term conditions which need to be supported and managed at home.
"So the challenge today is to provide integrated, coordinated, out of hospital care. Something where the NHS, with our tradition of family doctors and primary care, could lead the world."
However, a new study has warned that the NHS might not make its next milestone unless officials take "courageous action" to transform the service.
The health service faces "significant financial and demand pressures", said Mike Farrar, head of the NHS Confederation.
He said there needs to be a "radical shift" in the way the health service delivers care.
Writing a foreword for a new report on the coming challenges for the NHS, Mr Farrar said: "Sixty-five years from its foundation, the NHS remains a great source of national pride. But the service today is under significant financial and demand pressures that, as this report explores, only look set to increase.
"The result is a decade ahead that will see the NHS facing challenges greater than any it has had to deal with in its lifetime - challenges that demand a radical shift in the way we think about health and how we deliver care.
"On the 65th anniversary of the NHS it is right that we celebrate its great achievements. But we must also look to the future and work together to set an agenda for change that meets the needs of the population it serves."
The new report, conducted by consultancy firm PricewaterhouseCoopers, concludes that the public, care providers, regulators, commissioners and policy makers must take "deliberate and courageous action" to transform the NHS or it may not exist in its current form in 10 years.
The report recommends that the NHS moves from "fragmented to integrated care".