Last Updated: Tuesday, 14 August 2007, 15:04 GMT 16:04 UK
The former Islamist sparked huge controversy and protests in a failed bid for the post earlier this year.
Critics, including the army, feared an erosion of secular values despite Mr Gul's reassurances to the contrary.
Mr Gul's AK Party dominates the Turkish parliament, which chooses the president in a run of votes starting on Monday.
"Protection of secularism is one of my basic principles," Mr Gul told a news conference on Tuesday after submitting his application to parliament.
"Nobody should worry about this."
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It's extremely important that Turkey maintain it's secular
government. It is the only power in the Middle East to be
a secular state.