| Country: | NZL |
| Type: | SH |
| Route: | 78 |
| Map Custom: | yes |
| Map Notes: | Map of State Highway 78 |
| Length Km: | 0.9 |
| Length Round: | 1 |
| Direction A: | West |
| Direction B: | East |
| Terminus A: | at Timaru (cnr Theodosia Street & Sefton Street East) |
| Terminus B: | Port of Timaru (cnr Port Loop Road & Marine Parade) |
| Previous Type: | SH |
| Previous Route: | 77 |
| Next Type: | SH |
| Next Route: | 79 |
State Highway 78 is a New Zealand State Highway connecting central Timaru with its port. It holds the record for New Zealand's shortest state highway, with a length of just over 900m (3,000feet).
State Highway 78 begins at State Highway 1 just north of the CBD. It follows Sefton Street East for 200m (700feet) to Stafford Street, where it becomes Port Loop Road. The road then proceeds northeast over the South Island Main Trunk Railway, before turning anticlockwise around a loop, passing under itself parallel to the railway line. The highway terminates at the intersection of Port Loop Road with Marine Parade. It is believed to be the only State Highway that crosses itself (not counting motorway on/offramps).[1]