The Hawaiian Islands are well known for having one of the highest documented percentages of endemic plants in the world. Hawaiian ferns and lycophytes represent a relatively large percentage of the endemic flora with approximately 74% of the native fern and lycophyte species considered endemic. In addition, at least 40 taxa are naturalized aliens. We present a new synopsis of the Hawaiian fern and lycophyte flora that includes new state and island records, recent taxonomic updates and problems, and a summary of known and hypothesized geographical origins of fern and lycophyte lineages. We also provide a checklist and access to an interactive key to the native and naturalized ferns and lycophytes of the Hawaiian Islands ( http://www.herbarium.hawaii.edu/lucid/ferns/introduction.html).