Live television footage showed the Korea Space Launch Vehicle-1 (KSLV-1) blasting off from the Naro Space Center at 16:00.
Shortly after, officials said the launch appeared to have been a success.
The operation comes weeks after North Korea used its own three-stage rocket to place a satellite into orbit, sparking international criticism.
South Korea’s 140-tonne rocket, known as Naro, was partly built domestically and partly in Russia, which has said it will partner with Seoul for three attempts.
Previous launch attempts in 2009 and 2010 failed, and this attempt has been postponed twice for technical reasons.
But officials said Wednesday’s launch from the site 480 km (298 miles) south of Seoul had gone as planned, Yonhap news agency reports, and that the rocket had reached its target altitude and deployed its satellite.
“The launch of the rocket itself succeeded,” an official told Yonhap. But he said it was not yet possible to determine whether the satellite was in its correct orbit.
The satellite, called Science and Technology Satellite-2C, is designed to collect climate data. It is expected to make contact with its ground station at 05:00 on Thursday, at which point its operators will be able to determine whether it is in the right place and functioning properly.
Two warships with advanced radar equipment have been deployed to track the operation, says Yonhap.
South Korea does already have satellites in space, but they were launched from other countries.
On its first attempt to carry out a launch on its own soil, in 2009, the satellite failed to detach from the rocket in orbit. In 2010, the rocket exploded seconds after take-off.
Pressure for success has increased since North Korea launched a rocket that placed a satellite in orbit on December 12. It followed the launch by announcing plans for a “high-level nuclear test” and more long-range rocket launches.
The UN said the North Korean launch constituted a banned test of missile technology and voted to extend sanctions against Pyongyang. There have been international calls for Pyongyang not to carry out the nuclear test.
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