Otoyol 1 (English: Motorway 1), abbreviated as O-1 and locally referred to as The First Beltway^[1] (Turkish: 1. Çevreyolu), is a controlled access highway in Istanbul, Turkey. The O-1 serves as the inner beltway and is one of three intercontinental motorways in the city, the others being the O-2, and O-7, as well as connecting the European and Asian parts of the city via the Bosphorus Bridge.

It starts Osmaniye neighborhood in Bakırköy district on the European part, runs through the city over the Golden Horn and the Bosphorus, and terminates in Söğütlüçeşme neighborhood of Kadıköy district on the Asian part. Otoyol 1 is toll-free, however the Bosporus Bridge is a toll bridge in both directions, having its toll plaza at the Asian side. The O-1 is connected via three feeder highways to The Second Beltway.

Province	District	km	mi	Exit	Destinations	Notes
Istanbul	Bakırköy	0.0	0.0	K1	Osmaniye junction D.100-	northbound Mehmetakif cd.southbound Ekremkurt Blv.
	Zeytinburnu	2.6	1.6	K2	Topkapı junction	northbound exit. southbound entrance
		4.4	2.7	K3	Vatan caddesi junction	southeastbound Fatih, nourthwestbound Bayrampaşa
	Eyüpsultan	5.2	3.2	K4	Edirnekapı junction	southeastbound Fatih
		6.1	3.8	K5	Ayvansaray junction	southeastbound Fatih
	Golden Horn	6.5	4.0	Haliç Bridge
	Beyoğlu	7.2	4.5	K6	Halıcıoğlu junction
	Kağıthane	8.8	5.5	K7	Okmeydanı junction	Hasdal O-2 — Okmeydanı connector
	Şişli	10.9	6.8	K8	Çağlayan junction	southbound Piyalepaşa Blv.
	Beşiktaş	13.8	8.6	K9	Barbaros junction	nourthbound Büyükdere Cd.- O-2 connection path, southbound Barbaros Blv.
		15.1	9.4	K10	Balmumcu junction	Barbaros Blv.
	Bosphorus	16.3	10.1	Bosphorus Bridge (₺47.00 toll:13/01/2025)
	Üsküdar	18.2	11.3	K11	Beylerbeyi junction
		19.5	12.1	K12	Altunizade junction	eastbound Ümraniye- O-2 connection path
		21.4	13.3	K13	Çamlıca junction	O-2, O-4 Kocaeli Province Ankara
		22.8	14.2	K14	Uzunçayır junction	D.100 Kocaeli Province Ankara
	Kadıköy	24.8	15.4	K15	Söğütlüçeşme junction	Bağdat Cd.
1.000 mi = 1.609 km; 1.000 km = 0.621 mi        Tolled

• List of highways in Turkey

• Istanbul road map