J. Eng. Technol. Sci., Vol. 52, No. 3, 2020, 331- 342 331 Received August 15 th , 2019, Revised December 27 th , 2019, Accepted for publication May 18 th , 2020. Copyright ©2020 Published by ITB Institute for Research and Community Services, ISSN: 2337-5779, DOI: 10.5614/j.eng.technol.sci.2020.52.3.3 Extreme Significant Wave Height of Western and Central Indonesian Seas and Its Correlation with ISO 19901-1:2015 Andojo Wurjanto*, Julfikhsan Ahmad Mukhti, Hijir Della Wirasti, & Yosinta Eka Widyaningtias Ocean Engineering Program, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung 40132, Indonesia *E-mail: andojowurjanto@gmail.com Highlights:  The SEAFINE-based extreme significant wave height ranges from 4.5 to 5.5 m near the northern part of Natuna island for a 1-year return period and is approximately doubled for a 100-year return period.  In the Indonesian inner seas such as the Java Sea, the significant wave height ranges from 0.5 to 2.5 m for a 1-year return period and 1.5 to 5.0 m for a 100-year return period.  The SEAFINE-based 1-year and 100-year extreme significant wave heights are approximately 25% lower than that from ISO in intersecting regions. Abstract. Extreme significant wave height is a commonly used parameter for designing offshore structures. ISO provides general extreme significant wave height information of six ocean regions in the world, including the Southern East Asian Sea. However, for the case of Indonesia, ISO only includes the Natuna Sea region. One of the qualified datasets that provide significant wave height data for Indonesian seas is SEAFINE by Oceanweather, Inc. This dataset covers the western and middle parts of Indonesia. We analyzed the SEAFINE significant wave height hindcast data in these regions to obtain its extreme values. Extreme significant wave height maps were then produced based on the analyzed data. For validation, we compared the extreme value analysis result with ISO 19901-1:2015 in regions where SEAFINE and ISO data intersect. The comparison showed that the analysis result tends to give approximately 25% lower wave height compared to the ISO for the 1-year return period. The 100-year return period, however, highly agrees with the ISO. The analysis result also shows in line with previous studies in the Karimata Strait and the Java Sea. Keywords: Asia; ISO; metocean; SEAFINE; significant wave height. 1 Introduction Indonesia has 6.4 million km 2 of water area, accounting for about 77% of the total Indonesia area [1]. This relatively large water area has many potentials, such as maritime transportation, fisheries, ocean energy, mineral resources, and tourism