In recent years, the general interest in the safety of dams and reservoirs has grown appreciably. This research describes the application and design of labyrinth weirs to improve the performance of existing reservoirs and also to be used for the construction of new dams. The parameters that can affect the performance of labyrinth weirs are discussed. Tests were conducted on normal linear weirs with four different crest shapes to determine the rate of change of discharge coefficient when each type of weir is used. It is found that weirs with rounded-crest shape can pass more flow than other types of weirs when they are subjected to the same total operating head. Two design charts are developed for labyrinth weirs with rounded-crest shape with HT/P ratio ranges from 0.15 to 0.5 and 0.5 to 1.0. The areas of application of labyrinth weirs, design procedure, different cases of design, and a design example are given. In addition, the performance of labyrinth weirs when the structure placed in an angle to the approaching flow (inclined labyrinth weirs) was tested.