Citizens of most countries require valid visa to enter the Turkey. The Turkish Consulate General determines the duration of visa upon receiving an application.
eVisa for Tourism or Commerce
As of April 17, 2013, electronic visa (e-Visa) replaces “sticker visa” which was issued at the border crossings.
An e-Visa is an official document permitting entry into and travel within Turkey.
The e-Visa is an alternative to visas issued at Turkish missions and at the ports of entry.
Citizens of these countries are eligible to apply for e-Visa: Antigua and Barbuda, Armenia, Australia, Austria Bahamas, Bahrain, Barbados, Belarus, Belgium, Canada, Croatia, Dominica, Dominican Republic,Greek Cypriot Administration, Grenada Haiti, Hong Kong, Hungary, Indonesia, Ireland, Jamaica,Kuwait, Maldives, Malta, Mauritius, Netherlands, Norway, Oman, Poland, Portugal, Qatar, Saint Lucia,Saint Vincent and the Grenadines, Saudi Arabia, Slovakia, South Africa, Spain, U.S.A, United Arab Emirates, United Kingdom.
Please note that e-visa is only valid when the purpose of travel is tourism or commerce. Other purposes, such as work and study, require regular visa given by Embassies or Consulates.
Short Visits for Tourism
In general – depending on nationality and passport type – the following tourist visas are issued:

• Single entry visa: allows the holder to enter Turkey once, and stay in the country for up to three months (90 days). The visa is valid for use for one year from the date of issue
• Multiple entry visa: valid for up to five years and allows the holder to make multiple visits of up to three months each time
• Transit visa: valid for up to three months and permits travel through Turkish territory

Visitors coming to Turkey on an organized cruise do not need a visa for a visit of up to 72 hours. A visa is not needed when transiting – and remaining in the transit lounge – at a Turkish airport. A visa is needed if departing the airport transit area.
Visa to Work in Turkey
A work visa is only issued if the applicant has a signed job contract from a Turkish company and a work permit issued by the Ministry of Labour and Social Security – MLSS (Çalışma ve Sosyal Güvenlik Bakanlığı). The application process is made through the Turkish mission in the country of residence. It may take up to two months for the issue of the visa.
A work visa is valid for single entry.  Within 30 days of arrival in Turkey, the visa holder should apply for a residence permit at the Foreigner’s Division/Alien’s Branch of Local Police Department (Emniyet Müdürlüğü Yabancılar Şubesi). This allows multiple entries without the need of a visa for the duration of its validity.
Education Visas
It is obligatory to enroll in a Turkish university, school or certified language course before applying for an education visa. The letter of acceptance from the institution is required for the application. The visa application is made at the Turkish mission before leaving for the country; an education visa is generally valid for one year for single entry.
Within 30 days of arrival in Turkey, the visa holder may apply for a residence permit. This allows multiple entries for the period of validity.
Visa to Live in Turkey
If the intention is to move to Turkey to live, the relevant visa (work, education) is required to enter the country. Then a residence permit may be applied for within 30 days of arrival.
A person moving to Turkey to for other reasons (retirement, marriage, long stay) may enter on a tourist visa but must apply for residency within 30 days of arrival. The residency application must have the relevant supporting documentation for example proof of finances, accommodation, and marriage. A valid residence permit allows for multiple entries to Turkey with no visa required.