The projects, which will have nearly 20 million pounds ($27.54 million) of government funding, will focus on better understanding the condition, identifying effective treatments and the best ways to care for those suffering from it.
People with long COVID can have symptoms ranging from fatigue and brain fog to breathlessness and organ damage, experts have said.
"This package of research will provide much needed hope to people with long-term health problems after COVID-19," said Nick Lemoine, chair of the National Institute for Health Research's long COVID funding committee.
One study, at University College London, will recruit more than 4,500 people with long COVID to test the effectiveness of existing drugs as treatments over three months to see the impact on symptoms, mental health and the ability to return to work.
It will also look at whether MRI scans can be used to diagnose organ damage.
Another study at Cardiff University will look at whether the condition is caused by overactive or impaired immune responses, while research at Leeds, Oxford and Glasgow will examine the best care regime, the causes of breathlessness and the impact of obesity among people with long COVID, respectively.
The government has previously announced 100 million pounds for services to support those with long COVID, with 80 assessment services open in England so far.
"This new research is absolutely essential to improve diagnosis and treatments and will be life-changing for those who are battling long-term symptoms of the virus," health minister Sajid Javid said.
($1 = 0.7261 pounds) Reporting by Alistair Smout Editing by Helen Popper