Sea Launch is the world's sole company to orbit satellites from a pad in equatorial waters.
"At 12:50 a.m. Pacific Daylight Time (07:50 a.m. GMT), a Russian-made Zenit-3SL carrier rocket with the Galaxy 16 communications satellite was successfully launched from the Odyssey floating platform in the Pacific," Sea Launch said.
The launch was previously scheduled for June 17 but was delayed for one day for technical reasons.
The satellite will replace the old Galaxy 4R satellite, which belonged to PanAmSat. It is intended for broadcasts in the United States, Alaska, Hawaii, Mexico and Canada. Galaxy 16 is the fourth spacecraft Sea Launch will orbit for PanAmSat.
Sea Launch was created in 1995 as a consortium comprising Boeing, Norway's Kvaerner Group, leading Russian spacecraft-maker Energia, and Ukraine's Yuzhnoye design bureau and Yuzhmash production association.
It is the only company to operate launches from a sea platform in the Pacific's equatorial waters, a location that makes it possible to launch heavier payloads than from elsewhere.
Sea Launch made four successful launches in 2005 and one in 2006.