AbstrakPemahaman konsep matematika siswa masih rendah. Hal ini mengindikasikan bahwa proses pembelajaran di kelas belum maksimal. Penelitian ini termasuk penelitian tindakan kelas (PTK) yang dilakukan dengan maksud ingin meningkatkan pemahaman konsep matematika siswa melalui pengaplikasian model pembelajaran Two Stay Two Stray berbantuan Mind Mapping. Siswa kelas X MIA 1 dengan kemampuan yang heterogen berjumlah 34 orang dipilih menjadi subyek dari penelitian ini. Penyelenggaraan penelitian dilakukan di SMA Negeri 11 Makassar. Kegiatan penelitian dilakukan dalam 2 siklus yang setiap siklus mempunyai tahapan yakni perencanaan, pelaksanaan, pengamatan, serta refleksi. Pengumpulan data dilakukan dengan prinsip observasi dan tes yang diberikan pada setiap akhir siklus. Data yang sudah terkumpul dianalisis dengan analisis kualitatif dan kuantitatif. Hasil yang didapatkan secara kualitatif mengalami perubahan, siswa menjadi antusias mengikuti pembelajaran. Sementara hasil analisis kuantitatif menunjukkan bahwa secara menyeluruh terjadi kemajuan pada pemahaman konsep matematika siswa setelah mengaplikasikan pembelajaran Two Stay Two Stray yang berbantuan Mind Mapping.Abstract Students' understanding of mathematical concepts is still low. This indicates that the learning process in the classroom is not optimal. This research includes classroom action research (CAR) which was conducted with the intention of increasing students understanding of mathematical concepts through the application of the Two Stay Two Stray (TSTS) learning model. Students from class X MIA 1 with heterogeneous abilities amounted to 34 people were chosen to be the subjects of this study. The research was conducted at SMA Negeri 11 Makassar. The research activity was carried out in 2 cycles, each cycle having stages, namely planning, acting, observing, and reflecting. Data collection was carried out using the principle of observation and tests given at the end of each cycle. The collected data were analyzed using qualitative and quantitative analysis. The results obtained were qualitatively changed, students become enthusiastic about participating in learning. Meanwhile, the results of the quantitative analysis show that overall progress has occurred in the understanding of students mathematical concepts after applying to learn Two Stay Two Stray which is assisted by Mind Mapping.