Gülüm will join the Reds for the 2017/18 A-League season after spending the majority of his career with Turkish Süper Lig giants Beşiktaş.
The 30-year-old notched up 126 appearances with the Black Eagles in all competitions from 2010 to 2016, scoring three goals in the process.
Born in Melbourne to Turkish parents, Gülüm represented Turkey on the international stage and has earned seven caps since his debut in 2013. But Gülüm qualifies as an Australian through his dual-nationality and won't not count as a foreign player in the squad.  
Gülüm transferred to Turkish outfit Manisaspor from Hume City in 2005, before plying his trade in the second division briefly with Elazığspor and then Adanaspor for two seasons.
After signing for the Reds, Gülüm spoke of his delight at coming back to Australia to play and his excitement to play under Head Coach, Marco Kurz. 
"I am very happy to have signed for Adelaide United and cannot wait to get started," Gülüm said. 
"I've heard great things about the city and I'm really looking forward to working in a professional environment under a strong, European manager, like Marco. 
"I'm joining Adelaide with the ambition of being successful and I have every intention of making sure that happens. 
"Australian football has given me so much and I'm here to give back to it by working very hard every day in training." 
Kurz hailed the signing of Gülüm and the leadership qualities he will bring to the team.
“Gülüm is an experienced player who’s established himself in Turkey, where he’s captained the club and is clearly a leader,” Kurz said.
“I knew of him from his time in Europe with Beşiktaş, and I have no doubt he will be an excellent signing for the club. 
“I spoke with a teammate of Ersan’s during his time at Besiktas, a German player, who praised him highly.
"This is the first signing we have completed and is just the beginning of what we are aiming to do. 
"I am sure we will have more good news in the coming days." 
United's General Manager Ante Kovacevic said Gülüm will provide experience to the Reds in the heart of the defence.
“Enticing a player of this calibre back to the A-League is not a simple process. There are plenty of hurdles to get over, but thankfully we have finalised the deal," he said.
“He’s going to bring a lot of experience from his time in a top European league, that will benefit any A-League team.”