Development of E-Modul Based on Flip PDF Professional Application in Natural Science Subject, Subtheme 2 Heat Transfer. Interesting teaching materials can encourage student learning motivation, one of which is by using e-modules. Therefore it is necessary to develop an e-module. This study aims to develop an e-module teaching material product based on the Flip PDF Professional application in Natural Sciences Subject Subtheme 2 Heat Transfer. The research method used is Research and Development (R&D) using the ADDIE research model (Analysis, Design, Development, Implementation, Evaluation). This research begins with a needs analysis to find out the initial needs, e-module design, e-module development, and conducting validation tests on media experts, linguists, and material experts. This research was conducted at SDN Cikuda 03 in class V. The results showed that the e-module based on the Flip PDF Professional application that was developed had very feasible criteria. This is based on the percentage of media experts 96%, linguists 93%, material experts 96%, and student responses with an average gain of 90%. Based on the results of this study, it can be concluded that the developed Flip PDF Professional application-based e-module teaching materials are very appropriate for students to use in learning. Keywords: E-Modul, Flip PDF Professional, Natural Science, Heat Transfer. ABSTRAK Pengembangan E-Modul Berbasis Aplikasi Flip PDF Professional Pada Mata Pelajaran Ilmu Pengetahuan Alam Subtema 2 Perpindahan Panas. Bahan ajar yang menarik dapat mendorong motivasi belajar peserta didik, salah satunya dengan menggunakan e-modul. Oleh karena itu perlu adanya pengembangan e-modul. Penelitian ini bertujuan untuk mengembangkan produk bahan ajar e-modul menggunakan aplikasi Flip PDF Professional Pada Mata Pelajaran Ilmu Pengetahuan Alam Subtema 2 Perpindahan Panas. Metode penelitian yang digunakan yaitu Research and Depelopment (R&D) dengan menggunakan model penelitian ADDIE (Analysis, Design, Development, Implementation, Evaluation). Penelitian ini diawali dengan analisis kebutuhan untuk mengetahui kebutuhan awal, desain e-modul, pengembangan e-modul dan melakukan uji validasi kepada ahli media, ahli bahasa, dan ahli materi. Penelitian ini dilaksanakan di SDN Cikuda 03 di kelas V. Hasil penelitian menunjukkan e-modul berbasis aplikasi Flip PDF Professional yang dikembangkan memiliki kriteria sangat layak. Hal ini didasarkan pada presentase ahli media 96%, ahli bahasa 93%, ahli materi 96%, dan respon peserta didik dengan perolehan rata-rata 90%. Berdasarkan hasil penelitian ini dapat disimpulkan bahwa bahan ajar e-modul berbasis aplikasi Flip PDF Professional yang dikembngkan sangat layak untuk digunakan peserta didik dalam pembelajaran.