Penelitian ini bertujuan untuk mengetahui : pengaruh disiplin belajar terhadap prestasi belajar matematika siswa; pengaruh lingkungan keluarga terhadap prestasi belajar matematika siswa; pengaruh disiplin belajar dan lingkungan keluarga terhadap prestasi belajar matematika siswa kelas viii smp negeri 9 tarakan. penelitian ini dilaksanakan pada semester genap tahun ajaran 2020/2021. jenis penelitian yang digunakan adalah penelitian kuantitatif dengan metode survey. sampel dalam penelitian ini berjumlah 156 siswa di kelas viii smp negeri 9 tarakan. teknik pengumpulan data dalam penelitian ini dengan menyebarkan kuesioner disiplin belajar dan lingkungan keluarga secara online menggunakan goggle form dan dokumen penilaian tengah semester (pts) semester genap tahun ajaran 2020/2021. data yang diperoleh diolah dengan program pengolahan statistik yaitu menggunakan aplikasi spss 21.0. hasil penelitian ini menunjukkan bahwa terdapat pengaruh secara parsial antara disiplin belajar terhadap prestasi belajar matematika siswa kelas viii smp negeri 9 tarakan dengan persamaan regresi ?1 = 65,338 – 0,009 x1, dan terdapat pengaruh secara parsial lingkungan keluarga terhadap prestasi belajar matematika siswa kelas viii smp negeri 9 tarakan dengan persamaan regresi ?2 = 48,915 + 0,201 x2. selain itu hasil penelitian menunjukkan terdapat pengaruh yang signifikan secara simultan antara disiplin belajar dan lingkungan keluarga terhadap prestasi belajar matematika siswa kelas viii smp negeri 9 tarakan, dengan persamaan regresi ? = 55,395 – 0,0165x1 + 0,284x2. berdasarkan hasil perhitungan koefisien determinasi diketahui disiplin belajar dan lingkungan keluarga secara simultan memberikan pengaruh sebesar 1,7 % terhadap prestasi belajar matematika siswa kelas viii smp negeri 9 tarakan. kata kunci: disiplin belajar, lingkungan keluarga, prestasi belajar matematika

The objective of the research was to determine the effect of learning discipline on students mathematics learning achievement; the effect of the family environment on students’ mathematics learning achievement; the effect of learning discipline and family environment on mathematics learning achievement of eight grade students of smpn 9. this research was conducted in the even semester of the 2020/2021academic year. the type to the research was quantitative research with methods. the samples were taken by using the probablity sampling technique. the number of sample was 156 students at class viii of smpn 9 tarakan. the technique of collecting data was by distributing the questionnaires of learning discipline and family environment using a goggle form and the documents of mid-semester assesment (pts) for the even semester of the 2020/2021 academics year. the data obtained were analyzed by using a statistical program in the spss 21.0 application. the result of the research indicated that there was a partial effect between learning discipline on mathematics learning achievement of eight grade students of smpn 9 tarakan with the regression equation 1 = 65.338 – 0.009 x1, and there was a partial effects of family environment on mathematics learning achievement of eight grade students of smpn 9 tarakan with regression equation 2 = 48.915 + 0.201 x2. hence, the results of the research showed that there was a simultaneous significant effect between learning discipline and family environment on the mathematics learning achievement of eighth grade students of smpn 9 tarakan, with the regression equation = 55.395 + 0.0165x1 + 0,284x2. based on the results of calculation of the coefficent of determination, it was known that learning discipline and family environment simultaneously have an effect of 1.7% on mathematics learning achievement of eighth grade students of smpn 9 tarakan. keywords: learning discipline, family environment, mathematics learning achievement