T4 Topkapı - Mescid-i Selam tram line (Turkish: T4 Topkapı - Mescid-i Selam tramvay hattı) is a light rail line in Istanbul, Turkey, operated by Istanbul Ulaşım AŞ.

It runs from Topkapı north to Mescid-i Selam, a total of 15.3 km (9.5 mi).

After additional rolling stock was added however these trains were moved to operate on the M1 line.

Same vehicles used in on the Adana Metro and very similar to the LRTA 1100 class in Manila, Philippines.

More recently (from 2014) new high-floor trams that were constructed by Metro Istanbul (the operator) itself are also used.