ABSTRAK Penelitian ini bertujuan untuk mengetahui hasil uji validasi bahan ajar elektronik yang dibuat menggunakan Flip PDF Professional pada materi Alat-Alat Optik. Penelitian ini termasuk penelitian dan pengembangan (R&D) Model pengembangan yang digunakan yaitu model 3 D dengan langkah- langkah Define, Design, dan Develop. Validasi dilakukan oleh 2 judgement ahli dan 2 praktisi untuk menilai produk yang dikembangkan dari aspek penyajian, isi, dan bahasa. Berdasarkan hasil uji validitas aspek penyajian didapatkan hasil persentase sebesar 78,12% dengan kategori sangat baik, aspek isi sebesar 81,88% dengan kategori sangat baik, aspek bahasa sebesar 82,81% dan aspek media sebesar 75 % dengan kategori sangat baik. Berdasarkan hasil tersebut, dapat disimpulkan bahwa bahan ajar elektronik menggunakan Flip PDF Professional yang dihasilkan sudah valid dengan persentase total sebesar 79,45% yang termasuk dalam kategori sangat baik.Kata Kunci : Pengembangan dan penelitian, Bahan Ajar Elektronik, Flip PDF Professional ABSTRACT This research was aimed to describe validity tests of electronic teaching materials using Flip PDF Pro on Optical Instruments topic. This research used research and development model, namely 3D Development .The steps of 3D development were Define, Design, and Develop. Validation was carried out by 2 expert judgments and 2 practitioners to assess products developed from aspects of presentation, content, and language. Based on the results of the validity of the presentation aspects, the percentage results were 78.12% with very good categories, content aspects 81.85% with very good categories, language aspects at 82.75% and media aspects at 75% with very good categories. Based on these results, it can be concluded that the electronic teaching materials using Flip PDF Professional developed were valid and tested product with total validity test 79.4%, which is included in the excellent category.Keywords :Research and Development, Electronic Teaching Materials, Flip PDF Professional