The top 1% of reviewers in each of the 22 Essential Science Indicators (ESI) research fields. Rankings are calculated by number of verified pre-publication reviews performed and added to Publons between 1 September 2018 and 1 September 2019. Reviews were attributed to an ESI field based on the journal the review was performed for. We added a 22nd field, "Cross-field" to celebrate reviewers whose contributions were for the small amount of journals on Publons that could not be directly matched to an ESI field.