The I-205 Transitway was a partially built busway along the wide right-of-way of the Interstate 205 freeway in Portland, Oregon. Although it never opened as a busway, its right-of-way is now in use by light rail lines.
The transitway, which was physically separate from the parallel freeway lanes, was planned in the mid- and late-1970s as part of the final segment of I-205. Only a graded route with several entrance ramps and two underpass tunnels under I-205 were built. No bridges or overpasses were built until later adaptation for use by MAX Light Rail trains.
The transitway's right-of-way started in the median of I-205 near Portland International Airport and ran south to the junction of I-205 & I-84, where it continued through an underpass under the northbound lanes of I-205. From here it followed the freeway's east embankment to just south of Market Street, where it once again entered a tunnel taking it under the freeway. This tunnel took the right-of-way underneath all lanes (both directions) of I-205, surfacing west of the freeway's southbound lanes at a point just north of Division Street. From there, it continued south along the west side of I-205 to SE Foster Road, where it ended. The entire transitway has now been adapted for use by TriMet light rail trains.