Mr Ogan captured a surprising 5 per cent of the vote.
Mr Erdogan and Mr Kilicdaroglu will contest a run-off vote on May 28.
But who is Mr Ogan and what does he want? Here is what we know so far.
Who is Sinan Ogan?
Born to an Azerbaijani family in the small Turkish town of Melekli in 1967, Mr Ogan is the son of a farmer and the youngest in his family.
He completed his primary and secondary school education in the city of Igdir before studying business administration at Marmara University. He earned a master's degree in financial law in 1992.
In 2009, he was awarded a doctorate in international relations and political science by Moscow State University of International Relations.
During his youth, he was heavily active in politics, organising rallies and events to protest against the Soviets' massacre of civilians in Azerbaijan's capital Baku on January 20, 1990, now commemorated as Black January.
In 2011, he became a member of parliament after the Nationalist Movement Party won in local elections.
What party does he belong to?
Today, Mr Ogan represents nationalist, anti-refugee ideals, often claiming that Syrian refugees represent a national security threat to Turkey.
He is a member of the four-party right-wing Ancestral Alliance, which was established in March this year.
What is Ogan's role in Turkey's election?
In an interview with Reuters, Mr Ogan said he would back Mr Kilicdaroglu in run-offs if the second-placed candidate ruled out concessions to the Peoples' Democratic Party (HDP) pro-Kurdish party.
The left-wing HDP is accused of supporting Kurdish militias, a claim it rejects.
Turkey considers the Kurdistan Workers’ Party, or PKK, to be a terrorist group.
Mr Ogan has said he would not back any candidate “who doesn’t keep a distance with the terror organisation”.
The 2.8 million people who voted for Mr Ogan in the first round of elections could be crucial to the winning candidate in the run-offs.