Background: Until recently, little was known about the public’s knowledge of suicide or its association with help-seeking. Aims: In this article we describe the development, validation, and application of the Literacy of Suicide Scale (LOSS). Method: A total of 658 people participated in the development of the LOSS, while 191 participated in a validation study. Item response theory was used to identify LOSS items. A systematic review of the literature was conducted to ascertain the breadth of use and application of the LOSS. Results: Overall, 26 items were selected for the final version of the LOSS, with 12 items identified for a short form of the scale. The LOSS has been included in 25 studies across nine countries with general community, student, and clinical populations. The LOSS has demonstrated change in response to psychoeducation interventions and is associated with suicide stigma and help-seeking in select studies. Limitations: Further validation of the LOSS in clinical populations is needed. Conclusion: The LOSS is a comprehensive measure of suicide literacy that may be used to identify knowledge gaps, inform awareness-raising activities, and assess the effectiveness of interventions to improve suicide literacy. The LOSS has been used in a broad range of settings, demonstrating application to diverse populations and cultural contexts.