Penelitian ini menggunakan pendekatan kualitatif deskriptif yang bertujuan untuk menganalisis kemampuan penalaran matematis siswa SMA pada materi Pertidaksamaan Dua Variabel yang dikategorikan ke dalam lima kategori yaitu sangat baik, baik, cukup, kurang, dan sangat kurang. Subjek dalam penelitian ini yaitu siswa kelas X MIPA 3 di SMAN 2 Bantul sebanyak 31 siswa. Instrumennya yaitu instrumen tes kemampuan penalaran matematis dan wawancara. Bentuk tes kemampuan penalaran matematis yang disajikan sebanyak 2 butir soal dan wawancara kepada beberapa siswa yang terpilih pada setiap kategori. Berdasarkan hasil analisis tes kemampuan penalaran matematis dan wawancara diperoleh hasil sebesar 22,58% kategori sangat baik (7 siswa), 6,45% kategori baik (2 siswa), 48,39% kategori cukup (15 siswa), 16,13% kategori kurang (5 siswa), dan 6,45% kategori sangat kurang (2 siswa). This study uses a descriptive qualitative approach that aims to analyze the mathematical reasoning ability of high school students on the Inequality of Two Variables material which is categorized into five categories, namely very good, good, sufficient, less, and very poor. The subjects in this study were students of class X MIPA 3 at SMAN 2 Bantul as many as 31 students. The instruments are mathematical reasoning ability test instruments and interviews. The form of the mathematical reasoning ability test presented as many as 2 questions and interviews with several students who were selected in each category. Based on the results of the analysis of the mathematical reasoning ability test and interviews, the results obtained were 22.58% very good category (7 students), 6.45% good category (2 students), 48.39% sufficient category (15 students), 16.13% poor category (5 students), and 6.45% very poor category (2 students).