The provinces of Iran are divided more into counties called shahrestan (Persian: شهرستان shahrestān).  This is an area inside an ostan.  They usually contain a city center, a few bakhsh (Persian: بخش bakhsh), and a bunch of villages around them.  They are also usually some cities in each county.  As of the year 2005, Iran had 324 counties.

County list
The following is a list of counties by province:

Tehran Province
Damavand County  
Firuzkuh County   
Islamshahr County 
Karaj County 
Nazarabad County   
Pakdasht County       
Rebat-Karim County      
Rey County      
Savojbolagh County      
Shemiranat County     
Shahriar County      
Tehran County 
Varamin County

Qom Province
Qom County

Markazi Province
Ashtian County  
Arak County   
Delijan County
Khomein County   
Komeijan County   
Mahallat County   
Saveh County   
Shazand County  
Tafresh County 
Zarandieh County

Qazvin Province
Abyek County     
Buin-Zahra County
Qazvin County  
Takestan County

Gilan Province
Amlash County 
Astara County    
Astane-ye-Ashrafiyeh County 
Bandar-e-Anzali County
Fuman County 
Lahijan County 
Langrud County 
Masal County
Rasht County 
Rezvanshahr County 
Rudbar County 
Rudsar County
Shaft County
Siahkal County 
Some'e-sara County 
Talesh County

Ardabil Province
Ardabil County
Bilasavar County
Germi County
Khakhal County 
Kowsar County 
Meshginshahr County 
Namin County 
Nir County
Parsabad County

Zanjan Province
Abhar County    
Eejrud County   
Khodabandeh County   
Khorramdarreh County
Mahneshan County 
Tarom County
Zanjan County

East Azarbaijan Province
Ahar County
Ajabshir County
Azarshahr County               
Bonab County
Bostanabad County
Charuymaq County
Haris County
Hashtrud County
Jolfa County
Kalibar County
Malekan County
Maragheh County
Marand County
Mianeh County
Osku County
Sarab County
Shabestar County
Tabriz County
Varzaqan County

West Azarbaijan Province
Bukan County
Chaldoran County
Khoy County
Mahabad County 
Maku County 
Miandoab County 
Naqadeh County
Oshnavieh County 
Piranshahr County
Salmas County 
Sardasht County 
Shahindej County
Takab County
Urmia County

Kordestan Province
Baneh County   
Bijar County 
Divandarreh County 
Kamyaran County 
Marivan County
Qorveh County
Sannandaj County
Saqqez County 
Sarvabad County

Hamadan Province
Asadabad County   
Bahar County
Hamadan County
Kabudrahang County  
Malayer County  
Nahavand County
Razan County
Tuyserkan County

Kermanshah Province
Gilan-e-gharb County 
Harsin County
Islamabad-e-gharb County
Javanrud County
Kangavar County
Kermanshah County
Paveh County
Qasr-e-Shirin County
Sahneh County
Sarpol-e-Zahab County
Solas-e-Babajani County   
Sonqor County

Ilam Province
Abdanan County
Darrehshahr County       
Dehloran County
Eevan County  
Ilam County     
Mehran County     
Shirvan-o-Chardavol County

Lorestan Province
Aligudarz County
Azna County   
Borujerd County
Delfan County
Dorud County
Khorramabad County
Kuhdasht County
Poldokhtar County  
Selseleh County

Khuzestan Province
Abadan County
Ahvaz County  
Andimeshk County   
Baghmalek County
Behbahan County
Dasht-e-Azadegan County
Dezful County
Hendijan County
Izeh County
Khorramshahr County
Lali County   
Mahshahr County   
Masjed-Soleyman County 
Ramhormoz County   
Shadegan County   
Shush County   
Shushtar County

Chaharmahal and Bakhtiari Province
Ardal County     
Borujen County
Farsan County     
Kuhrang County    
Lordegan County  
Shahrekord County

Kohgeluyeh and Boyer-Ahmad Province
Bahmai County
Boyer-Ahmad County   
Dena County
Gachsaran County
Kohgeluyeh County

Bushehr Province
Bushehr County
Dashtestan County      
Dashti County    
Dayyer County      
Deylam County
Ganaveh County
Jam County   
Kangan County          
Tangestan County

Fars Province
Abadeh County    
Arsanjan County
Bavanat County
Darab County
Evaz County
Eqlid County
Estahban County  
Farashband County  
Fasa County  
Firuzabad County 
Jahrom County
Kazerun County 
Khorrambid County 
Lamerd County
Larestan County
Mamasani County 
Marvdasht County  
Mehr County  
Neyriz County 
Qir-o-Karzin County
Sepidan County  
Shiraz County
Zarrindasht County

Hormozgan Province
Abumusa County
Bandar-Abbas County
Bandar-Lengeh County
Bastak County
Gavbandi County
Hajiabad County
Jask County
Minab County   
Qeshm County
Rudan County

Sistan and Baluchestan Province
Chabahar County 
Iranshahr County 
Khash County
Nikshahr County
Saravan County  
Sarbaz County
Zabol County  
Zahedan County

Kerman Province
Anbarabad County 
Baft County
Bam County  
Bardsir County  
Jiroft County
Kahnuj County
Kerman County  
Manujan County
Rafsanjan County 
Ravar County  
Shahr-e-Babak County
Sirjan County    
Zarand County

Yazd Province
Abarkuh County   
Ardekan County 
Bafq County
Khatam County
Mehriz County 
Meybud County
Sadugh County
Tabas County 
Taft County
Yazd County

Esfahan Province
Aran-o-Bidgol County   
Ardestan County 
Borkhar-o-Meymeh County
Chadegan County
Falavarjan County 
Fereydan County  
Fereydunshahr County
Golpayegan County  
Isfahan County
Kashan County
Khansar County
Khomeinishahr County  
Lenjan County
Lower Semirom County
Mobarakeh County  
Nain County 
Najafabad County  
Natanz County
Semirom County   
Shahreza County    
Tiran-o-Korun County

Semnan Province
Damghan County
Garmsar County  
Semnan County  
Shahrud County

Mazandaran Province
Amol County  
Babol County 
Babolsar County 
Behshahr County
Chalus County
Juybar County 
Mahmudabad County 
Neka County
Noshahr County
Nur County 
Qaemshahr County
Ramsar County 
Sari County 
Savadkuh County
Tonekabon County

Golestan Province
Aliabad County
Aqqala County
Azadshahr County   
Bandar-e-gaz County  
Bandar-e-Torkaman County
Gonbad-e-Kavus County
Gorgan County 
Kolaleh County   
Kordkuy County
Minudasht County  
Ramian County

North Khorasan Province
Bojnurd County 
Isfarayen County   
Jajrom County
Maneh-o-Samalqan County     
Shirvan County

Razavi Khorasan Province
Bardaskan County
Chenaran County
Dargaz County
Fariman County
Gonabad County
Kalat County
Kashmar County
Khaf County
Khalilabad County
Mashhad County
Neyshabur County
Qaenat County
Quchan County
Rashtkhar County 
Sabzevar County
Sarakhs County
Taybad County
Torbat-e-Jam County
Torbat-e-Heydarieh County

South Khorasan Province
Birjand County       
Darmian County
Ferdows County
Nehbandan County
Qaen County 
Sarayan County 
Sarbisheh County

 
Lists of counties
Iran-related lists