The Tazlău is a left tributary of the river Trotuș in Romania. Its source is in the Tarcău Mountains. It discharges into the Trotuș in Onești. The Belci Dam, which failed in 1991, was built on the Tazlău River. The following villages are situated along the river Tazlău, from source to mouth: Tazlău, Frumoasa, Balcani, Ludași, Pârjol, Tărâța, Hemieni, Scorțeni, Tescani, Berești-Tazlău, Sănduleni, Livezi, Helegiu and Slobozia.