Monitoring butterflies is one of the oldest examples of citizen science. The success of Butterfly Monitoring Schemes (BMS’s) is due to many factors, not least that the techniques are easy to learn and the field work fun to do. The results of such schemes have proven invaluable in providing robust data on changes in butterfly populations in nature reserves, local areas, countries and even whole regions, such as Europe. Therefore, each individual recorder becomes part of a joint effort to track butterfly fauna and biodiversity in their local area, country, region, and even the whole world as we plan to move towards a Global Butterfly Index. Currently butterfly monitoring is well established in temperate regions such as Europe and North America. The focus of these guidelines is to outline generic field protocols for monitoring butterfly populations (as opposed to species inventories or distributions) that can be applied in any part of the world. Thereby, these guidelines will enable the growth of butterfly monitoring around the world and make possible the creation of a Global Butterfly Index. The proposed Global Butterfly Index would be similar to, or could feed into, the Living Planet Index (McRae et al., 2014), one of the most well-known biodiversity indicators, that measures the state of biodiversity and highlights trends in thousands of vertebrate species populations over large regions of the world. Furthermore, population abundance of species is one of the Essential Biodiversity Variables recently proposed as a minimum set of essential measurements to capture major dimensions of biodiversity change (Pereira et al., 2013).