The test, which can be ordered online, uses a small droplet of blood that is sent to a laboratory.
Public Health England (PHE) is urging more people to check their HIV status.
It says four in 10 people in the UK are diagnosed late - meaning treatment may be less effective and the disease can be spread unwittingly.
Official figures for 2014 show 103,700 people have HIV in the UK.
And though rates are falling overall, PHE warns it is still a growing problem in certain communities.
Experts say improved treatment means that if people are diagnosed early on, they can have a life-expectancy that almost matches those who are HIV free.
Prof Kevin Fenton, at PHE, added: "With national HIV-testing week approaching, I would encourage all those at higher risk of HIV, such as men who have sex with men or people from black African communities, to seriously consider testing, especially as they are now able to order a home sampling kit free online."
The kit involves a finger-prick blood test that is sent off to be analysed. Three to five days later, people are contacted with results.
If the test suggests HIV is likely, patients are asked to attend a sexual health clinic for a confirmatory check.
The free test will be available to anyone in England until 1 January 2016.
After this, local authorities will have to make individual decisions regarding funds. Some have already been attempting trials of other free home-tests.
A separate, commercial do-it-yourself kit was launched earlier this year, which works in a similar way to a pregnancy test - providing rapid results.
But charities warn efforts to tackle HIV have been hit by funding cuts.
Deborah Gold, chief executive of the National Aids Trust, said: "We need to scale up our HIV testing and prevention efforts, but instead the government cut millions off the budget this year used to pay for both."
According to the latest HIV figures:
A free HIV home-testing kit has been launched across England as the latest figures show 18,100 people in the UK are unaware they have the infection.