|Full name||Konstantinos Nikolaos Giannoulis|
|Date of birth||9 December 1987|
|Place of birth||Katerini, Greece|
|Height||1.83 m (6 ft 0 in)|
|Playing position||Left back|
|2006||→ Fostiras (loan)||0||(0)|
|2006–2007||→ Pierikos (loan)||25||(0)|
|2010–2011||1. FC Köln||0||(0)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 4 May 2017.
‡ National team caps and goals correct as of 31 December 2015
Konstantinos Nikolaos Giannoulis (Greek: Κωνσταντίνος Νικόλαος Γιαννούλης; born 9 December 1987) is a Greek footballer who currently plays for Greek Superleague club Asteras Tripoli as a left-back.
He started his professional career in 2005 with Panionios, but he failed to make a single appearance for the club, and he was loaned to Fostiras and Pierikos. He made 25 appearances for Pierikos in their successful Gamma Ethniki campaign, where they won the title and promotion to Beta Ethniki.
In May 2010 he signed for Bundesliga side 1. FC Köln. Koeln have been quick to indicate their contentment with this deal. "We are very glad to have signed Konstantinos Giannoulis, who will be a gain for the defence," said general manager Michael Meier to the club’s official website. "He fits exactly our left back requirements for the coming season." Kicker reports that because of Iraklis ongoing financial difficulties, Koeln have been able to swoop for the defender by tabling a “low six-figure fee”. They were not the only German outfit interested in the full-back, as Kaiserslautern had already made concrete steps towards securing the Greek’s signature. After half a season however, having never played for the first team, he was told that he could leave the club for free.
On 23 June 2011, he agreed to sign a season-long loan deal with Greek Superleague side Atromitos, where he made 25 appearances and scored 1 goal. On 7 August 2012, Giannoulis was officially released by 1. FC Köln and subsequently signed a three-year contract with Atromitos.
On 28 June 2014, the 27 years old defender signed an extension of his contract (which ended at 2015) for another two years in presence of the Technical Director Mr. Giannis Aggelopoulos. He is the seventh football player that in a period less of a year that renews his contract with our team after Tasos Karamanos, Luigi Cennamo, Nikolaos Lazaridis, Efstathios Tavlaridis, Luiz Eduardo Santana Brito and Miguel Sebastián Garcia. Kostas Giannoulis a football player with ethics, quality and inexhaustible source of strength had the last season (2013/14) 44 appearances in all the organizations.
On 31 August 2014 it was announced that Kostas Giannoulis has joined Olympiacos. Giannoulis commented the following at atromitosfc.gr : "A great thank is nothing in front what I owe to Atromitos. After a bad year in Germany, Atromitos brought me in Greece and gave me the chance to participate in a high level and to show the talents that I have by playing at least only once in the National Team and now to achieve a transfer at the top club of the country." 
On 9 July 2015, he solved his contract with the club.
|2010–11||1. FC Köln||1. Bundesliga||0||0||0||0||0||0||0||0|
|2015–16||Asteras Tripoli||Superleague Greece||19||0||5||1||4||0||28||1|
|2016–17||Asteras Tripoli||Superleague Greece||26||0||4||0||0||0||30||0|
- "Atromitos signed Kostas Giannoulis". Eleftherotypia (in Greek). 23 June 2011.
- "Kostas Giannoulis statistics". onsports.gr (in Greek).
- "Atromitos on top". Eleftherotypia (in Greek). 22 October 2011.
- "Agios Dimitrios and Pierikos celebrate promotion". Protathlitis (in Greek). 28 May 2007.
- "Giannoulis to Koeln". Zougla.gr (in Greek). 25 May 2010.
- "Iraklis Left-Back Kostas Giannoulis Finalises Koeln Switch". goal.com. 28 May 2010.
- "Trio des 1. FC Köln kann in der Winterpause gehen" [1. FC Köln trio can leave in the winter break] (in German). Die Zeit. 16 December 2010. Retrieved 16 December 2010.
- "Kostas Giannoulis joins Atromitos FC". Atromitos FC. 23 June 2011.
- "Atromitos F.C. statistics". Superleague Greece. Retrieved 29 November 2011., ΓΙΑΝΝΟΥΛΗΣ ΚΩΣΤΑΣ (Greek)
- "Giannoulis returns "home"". Atromitos F.C. 7 August 2012. Retrieved 8 August 2012.
- "Kostas Giannoulis renew his contract until 2017!". atromitosfc.gr. 28 June 2014.
- Παίκτης του Ολυμπιακού ο Γιαννούλης (in Greek). olympiacos.org. 31 August 2014.
- Transfer of Kostas Giannoulis.
- Αποχαιρέτησε τον Ολυμπιακό ο Γιαννούλης (in Greek). www.sdna.gr. Retrieved 10 July 2015.
- Επίσημο: Ο Γιαννούλης στον Αστέρα (in Greek). www.sport24.gr. 15 July 2015.
- "Greece vs Romania line-ups". Goal.com. 15 November 2011.
- "ΕΛΛΑΔΑ - SUPER LEAGUE" (in Greek). www.sportdata.gr.