The M78 is a short metropolitan route in Greater Johannesburg, South Africa.

[1][2] It is a short route connecting Illiondale with Klopper Park in the Edenvale/Germiston area of Ekurhuleni Metropolitan Municipality.

[3] The M78 begins at a junction with the R25 road in the suburb of Illiondale (south of Modderfontein and north-east of Edenvale CBD).

It continues south as Harris Avenue, separating the Sebenza and Edenglen suburbs of Edenvale, to reach a junction with the M16 road (Baker Road) east of Edenvale CBD.

[3] The M78 proceeds to fly over the R24 highway (Albertina Sisulu Freeway) and enter Klopper Park (the northernmost suburb of Germiston), where it reaches a junction with the M99 road (Herman Street).