Otoyol 21

Otoyol 21 (English: Motorway 21), abbreviated as O-21, a.k.a. Ankara-Tarsus Otoyolu (English: Ankara-Tarsus Motorway), is a completed toll motorway in the Central Anatolia and Mediterranean regions in Turkey. Currently, it connects Otoyol 20 from Gölbaşı, Ankara with the Adana-Mersin Motorway O-51 at Tarsus in Mersin Province. On its full length, it is part of the European E90. The last part of the highway opened on 16 December 2020.^[1] With a length of 432 kilometres, the O-21 is the longest motorway in Turkey.

Province	District	km	mi	Exit	Destinations	Notes
Ankara	Gölbaşı	0.0	0.0	K8	O-20 (Ankara beltway) — Ankara
		14.4	8.9	K1	D.260 — Haymana, Ankara
		16.9	10.5	Gölbaşı Toll Plaza
		29.5	18.3	K2	D.750 — Ahıboz
		76.1	47.3	K3	D.753 — Kulu
	Şereflikoçhisar	101.5	63.1	K4	D.757 — Acıkuyu
Aksaray	Sarıyahşi	139.5	86.7	K5	P.68-83 — Sarıyahşi
	Ağaçören	157.5	97.9	K6	Kırşehir connector — Kırşehir
	Ortaköy	178.3	110.8	K7	D.757 — Kırşehir, Ortaköy
	Aksaray	213.6	132.7	K8	D.300 — Aksaray, Nevşehir
Nevşehir	Derinkuyu	241.6	150.1	K9	P.68-83 — Sarıyahşi
Niğde	Niğde	275	171	K10	P.51-78 — Gölcük
				K11	D.765 — Nevşehir
				K11	D.805 — Kayseri
				K12	D.805 — Niğde / Aydın Ave.
	Bor			K13	P.51-51 — Kemerhisar
	Ulukışla			K14	O-21A — Konya
				Kırkgeçit Tunnels
				Çakıt Tunnel
Adana	Pozantı			K15	D.750 — Pozantı	Pozantı north
				K16	D.750 — Pozantı	Northbound exit, southbound entrance only.
				K17	D.750 — Akçatekir
Mersin	Tarsus			K18	D.750 — Çamalan
				K19	O-51 — Mersin, Adana
				Tarsus Toll Plaza
				K20	D.400 — Mersin, Adana
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Incomplete access        Tolled       Unopened

• List of highways in Turkey

• Exit list of O-21
• Mersin road map Archived 2011-07-25 at the Wayback Machine