Aspirin is commonly used to help prevent heart attacks
The study estimates that 40,000 extra deaths world-wide could be prevented - 3,000 in the UK alone.
It says the drug, which reduces the risk of blood clotting, is massively underused in the treatment of patients suffering heart attacks and strokes.
The research team hopes their findings will help dispel any remaining uncertainty among doctors and lead to an increase in prescribing aspirin.
Angina
The study, published in the British Medical Journal, was funded by the British Heart Foundation (BHF) and the Medical Research Council (MRC).
It says that although the use aspirin is well-known in helping to prevent heart attacks and strokes, less than half of high-risk patients are prescribed the drug.
Aspirin and other blood-thinning drugs are almost always prescribed to patients who have suffered an acute heart attack or unstable angina - pain caused by insufficient blood reaching the heart muscle.
'Routine consideration'
But the new study says still more lives could be saved by using aspirin more widely.
Dr Colin Baigent, the MRC scientist who led the research: "This study shows that aspirin is beneficial in an even wider range of conditions than previously believed.
"What we now need is to ensure that aspirin, or some other anti-platelet drug, is routinely considered for patients who might need it."
Researchers reviewed 287 clinical trials involving 200,000 patients.
The work was co-ordinated by scientists from the Clinical Trial Service Unit at the University of Oxford.
The BHF says one of the main reasons for the under-use of aspirin could be a lack of clear advice on how effective the drug is in treating patients at risk of vascular disease, but who have not suffered a heart attack or stroke.
'Life-saving'
The researchers warned that aspirin is only suitable for those who are at increased risk of a heart attack or stroke for a special reason.
They urge people to consult their doctor before taking aspirin regularly.
Professor Sir Charles George, BHF medical director, said: "These findings reinforce what we have known for some time, that aspirin is a life-saving treatment that will provide major benefits to many thousands of people at high risk of heart attack or strokes.
"Aspirin is not an appropriate treatment for everyone, but it is important that all those who might benefit are actually offered it."
Dr Baigent said surveys in the UK have shown that aspirin is prescribed to less than a quarter of people with diseases such as peripheral arterial disease - a condition which causes fatty deposits to build up in the arteries of the leg, and which commonly leads to heart attacks or strokes.
The research also suggests that for normally healthy people, who are at a slightly increased risk for some reason, it remains unclear if the benefits of aspirin outweigh any risks.
Aspirin can also be used as a long term treatment for those with a history of heart attack and stroke, or who have peripheral arterial disease, stable angina or atrial fibrillation - an irregular heart rhythm.
In some cases, adding a second anti-platelet drug to aspirin seemed to give extra protection.