Penelitian ini dilatarbelakangi karena kurangnya aktivitas dan keaktifan peserta didik dalam proses pembelajaran. Tujuan penelitian ini untuk meningkatkan keaktifan belajar peserta didik dalam proses pembelajaran. Model pembelajaran yang digunakan peneliti adalah discovery learning dengan metode penilitian tindakan kelas sebanyak dua siklus. Setiap siklus dilaksanakan dalam dua kali pertemuan dengan empat tahap kegiatan yaitu perencanaan, pelaksanaan, pengamatan, dan refleksi. Subjek penelitian yaitu kelas IX F SMPN 21 Semarang yang berjumlah 33 peserta didik. Teknik pengumpulan data yang digunakan yaitu observasi, dokumentasi, dan tes. Hasil penilitian pra siklus menunjukkan bahwa hasil rata-rata keaktifan peserta didik pada presentase 49,29%, sedangkan pada fase siklus I presentase keaktifan peserta didik sebanyak 70,70%, dan meningkat lagi pada fase siklus II keaktifan peserta didik menjadi 76,56%. Maka dari itu dapat disimpulkan bahwa penggunaan discovery learning dapat meningkatkan keaktifan belajar peserta didik pada mata pelajaran IPS materi masa kemerdekaan Indonesia (1945-1950).   
This research was motivated by the lack of activity and activeness of students in the learning process. The aim of this research is to increase students' active learning in the learning process. The learning model used by researchers is discovery learning with a two-cycle classroom action research method. Each cycle is carried out in two meetings with four activity stages, namely planning, implementation, observation and reflection. The research subjects were class IX F of SMPN 21 Semarang, totaling 33 students. The data collection techniques used are observation, documentation and tests. The results of the pre-cycle research showed that the average percentage of student activity was 49.29%, while in the first cycle phase the percentage of student activity was 70.70%, and increased again in the second cycle phase, student activity was 76.56%. . Therefore, it can be concluded that the use of discovery learning can increase students' active learning in social studies subjects during the period of Indonesian independence (1945-1950).