In a first for space history, the spacecraft was manoeuvred alongside a speeding comet to begin mapping its surface in detail. The spacecraft fired its thrusters for six and a half minutes to finally catch up with comet 67P/Churyumov-Gerasimenko.
"We're at the comet!" said Sylvain Lodiot of the European Space Agency (Esa) operations centre in Germany.
"After 10 years, five months and four days travelling towards our destination, looping around the Sun five times and clocking up 6.4 billion km, we are delighted to announce finally 'we are here'," said Jean-Jacques Dordain, director general of Esa.
Launched on board an Ariane rocket in March 2004, Rosetta has taken a long route around our Solar System to catch up with comet 67P.
In a series of fly-pasts, the probe used the gravity of the Earth and Mars to increase its speed during the 6 billion km chase.
To save energy, controllers at the European Space Agency's centre in Darmstadt, Germany put Rosetta into hibernation for 31 months.
In January they successfully woke the craft from its slumber as it began the final leg of the daring encounter.
For the past two months Rosetta has been carrying out a series of manoeuvres to slow the probe down.
The comet is travelling at 55,000km per hour (34,175 mph). The spacecraft's speed has been adjusted so that in relative terms it will be flying beside the comet at a slow walking pace of 1m/sec (2.2mph, 3.6kph).