This category relates to:

1. Railway companies that are no longer operating under their own name (known as "fallen flags" in the US). They may have been purchased by other railroads, gone bankrupt, or been merged; and
2. Railway lines that have closed for use, usually being removed and sometimes obscured.

Wikimedia Commons has media related to Former railway lines.

There are a range of terms that are synonymous, including: closed railways, former railways