The Donnellys Crossing Section, also known as the Kaihu Valley Railway or Kaihu Branch, was a railway line in Northland, New Zealand. Initially an isolated line of 35.91 kilometres (22.31 mi), it became a branch line when the Dargaville Branch was opened and connected it with the North Auckland Line and the rest of the national rail network in 1943. The branch was closed in 1959.

The North Auckland Line is a major section of New Zealand's national rail network, and is made up of the following parts: the portion of track that runs northward from Westfield Junction to Newmarket Station; from there, westward to Waitakere; from there, northward to Otiria via Whangārei. The first section was opened in 1868 and the line was completed in 1925. The line, or sections of it, have been known at various times as the Kaipara Line, the Waikato-Kaipara Line, the Kaipara Branch and the North Auckland Main Trunk.