Ameobi, 32, was released by the Premier League outfit after 14 years at St James' Park, and after being linked with a move to the A-League in Australia, he was unveiled by Gaziantep on Monday.
"We want to establish an ambitious team in the league this season, and a strong team continues to strengthen by adding players," a statement on the 2.Lig side's website read.
"We have therefore tied Nigerian striker Shola Ameobi - from one of the strongest teams in England, Newcastle United - to us for one year."
Ameobi was a youth product at Newcastle before making 312 league appearances for the Tyneside outfit, scoring 53 goals.
The nine-time Nigeria international featured twice at the World Cup in Brazil, tallying 63 minutes, having previously represented the England Under-21 team from 2000-03.
Gaziantep finished 13th in the 2013-14 campaign in the Turkish second division.
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