ABSTRAK Peningkatan Keaktifan dan Hasil Belajar Matematika melalui Model Problem Based Learning Siswa Kelas V-B SD Negeri 74 Kota Bengkulu. Tujuan penelitian ini adalah (1) mendeskripsikan langkah-langkah penerapan model Problem Based Learning, (2) meningkatkan keaktifan, dan (3) meningkatkan hasil belajar matematika. Penelitian ini menggunakan teknik Penelitian Tindakan Kelas kolaboratif. Subjek penelitian ini adalah siswa kelas V-B berjumlah 26 siswa. Prosedur penelitian tindakan kelas berupa perencanaan, pelaksanaan, observasi dan refleksi. Pelaksanaan tindakan dilaksanakan dalam dua siklus masing-masing siklus dua pertemuan. Teknik pengumpulan data yang digunakan adalah observasi, wawancara, angket, dan tes. Validitas data menggunakan teknik triangulasi sumber dan triangulasi teknik. Analisis data menggunakan teknik analisis kuantitatif dan kualitatif, meliputi reduksi data, sajian data, dan verifikasi data. Hasilnya menunjukkan bahwa penerapan model Problem Based Leaning dapat meningkatkan keaktifan dan hasil belajar matematika pada siswa kelas V Sekolah Dasar. Kata Kunci: Problem Based Learning, Keaktifan, Hasil Belajar, Matematika ABSTRACT The Improvement Activity and Learning Result Mathematics through Problem Based Learning Model V-B Grade Students of State Elementary School 74 Bengkulu City. The purpose of this research are: (1) describing the application of Problem Based Learning models, (2) improving of activity, and (3) improving of learning result mathematics. This research is a Collaborative Classroom Action Research. Subject of this research is a students in V-B grade total 26 students. Procedure research are, action, observation, and reflection. There are in two cycle, each cycle two meeting. The data collection technique is testing the results of observation, interviews, questionnaires and tests. The validity of data using triangulation source and triangulation techniques. Data analysis using quantitative analysis techniques and qualitative analysis, including data reduction, presentation of data, and verification. The results show that the application of Problem Based Learning models can be improve the activity and learning result in mathematics elementary school fifth grade students. Keyword: Problem Based Learning, Activity, Learning Result, Mathematics