Jenis penelitian ini adalah deskriptif kualitatif yang dilaksanakan di jurusan PGSD FKIP Universitas Borneo Tarakan. Penelitian ini berfokus pada menganalisis kemampuan berpikir kritis mahasiswa PGSD Universitas Borneo Tarakan dalam menyelesaikan masalah geometri. Sumber data dalam penelitian ini berupa sumber data primer dengan partisipan yaitu mahasiswa lokal A3 PGSD angkatan 2021 yang telah menempuh mata kuliah geometri. Indikator kemampuan berpikir kritis yang digunakan yaitu interpretasi, analisis, evaluasi, kesimpulan, eksplanasi dan regulasi diri. Teknik pengumpulan data yang digunakan adalah tes berpikir kritis dan wawancara. Menggunakan teknik analisis data kualitatif melalui reduksi data, penyajian data, dan penarikan kesimpulan. Data hasil tes dikelompokkan berdasarkan 3 kategori yaitu baik, sedang dan rendah. Kemudian dipilih 6 perwakilan subjek berdasarkan kategori baik, sedang dan rendah untuk diwawancarai. Hasil penelitian menunjukkan subjek kategori berpikir kritis baik mampu memenuhi 6 indikator kemampuan berpikir kritis dengan benar. Subjek dengan kemampuan berpikir kritis sedang hanya mampu memenuhi 4 indikator berpikir kritis karena kurang memahami masalah dan konsep soal. Subjek dengan kemampuan berpikir kritis rendah tidak mampu memenuhi semua indikator berpikir kritis dengan benar.

Kata Kunci: Berpikir Kritis, Menyelesaikan Masalah, Geometri

This type of study carried out at PGSD Department FKIP Universitas Borneo Tarakan was a qualitative descriptive. The purpose of this study was to examine how PGSD Universitas Borneo Tarakan students employed critical thinking to solve geometric problems. The participants in this study were local A3 PGSD students from the class of 2021 who had completed geometry courses, and the data source was a primary data source. The markers of critical thinking were self-regulation, conclusion, conclusion, analysis, and evaluation. Critical thinking exams and interviews were two of the data collection methods employed. Utilizing methods for qualitative data analysis, including data reduction, data visualization, and conclusion-making. Data on test results were divided into three categories: good, medium, and low. Following that, six representative participants were chosen for interviews based on the good, medium, and low categories. The findings demonstrated that those who fell into the group of "excellent critical thinking" were able to accurately respond to each of the six markers of critical thinking skill. Because they did not comprehend the topic and its concept, subjects with moderate critical thinking skill could only satisfy 4 signs of critical thinking. Low critical thinking skill prevented students from accurately demonstrating all critical thinking signs. Keywords: Critical Thinking, Solving Problems, Geometry