Only civil marriage is legal in Turkey. You may have any religious ceremony you wish in addition to the civil one, but the religious service has no legal standing in Turkey.
Also, notice that Turkish officials cannot perform a marriage that would not be approved in your own country. If your own country's laws prohibit you from marrying, you will not be able to obtain from authorities of your own country the documents that are required by Turkish marriage law, and thus you will not be able to marry in Turkey.
Same Nationality
If both bride and groom have the same nationality and it is not Turkish, your marriage will be valid if conducted either byTurkish authorities or by your country's embassy or consulate officials. But note that not all embassies and consulates will perform marriages—check with yours.
For marriage by Turkish authorities, you must obtain a document from the authorities in your own country attesting to your eligibility for marriage. This can be a marriage license or a statement (Evlenme Ehliyet Belgesi) from your country's diplomatic officers (usually a consul) resident in Turkey. (See Additional Requirements and Necessary Documents).
Different Nationalities
If you and your fiancé(e) are of different nationalities, and neither of you is a Turkish citizen, your marriage must be conducted by a Turkish official. The foreign national must obtain a document from the proper authorities in his or her own country attesting to eligibility for marriage: a marriage license, or a statement (Evlenme Ehliyet Belgesi) from embassy or consular authorities resident in Turkey. (See Additional Requirements and Necessary Documents).
Foreigner Marrying a Turk
If one person is Turkish and the other is not, your marriage must be conducted by a Turkish official. You must obtain a document from the proper authorities in your own country attesting to your eligibility for marriage: a marriage license or statement (Evlenme Ehliyet Belgesi) from embassy or consular authorities resident in Turkey. (See Additional Requirements and Necessary Documents).
American(s) Marrying in Turkey
If one of the people being married is a citizen of the USA, click here for more tips.