Penelitian ini bertujuan untuk mengembangkan lembar kerja siswa (LKS) berbasis proyek untuk meningkatkan ketrampilan berpikir kritis siswa pada materi sistem pernapsan manusia di SMP Negeri 4 Tarakan yang layak berdasarkan penilaian para ahli dan mengetahui respons siswa terhadap lembar kerja siswa (LKS) berbasis proyek untuk meningkatkan ketrampilan berpikir kritis siswa pada materi sistem pernapasan manusia. Jenis penelitian ini adalah Research and Development (R&D) dengan desain penelitian model Borg & Gall (1983). Adapun langkah-langkah model model Borg & Gall (1983) yang digunakan dalam penelitian ini yaitu dimulai dari penelitian dan pengumpulan data awal, perencanaan, pengembangan prouk awal, uji coba produk awal dan revisi produk. Analisis data menggunakan pendekatan deskriptif kualitatif dan kuantitatif. Hasil pengembangan produk lembar kerja siswa (LKS) mendapatkan hasil validasi dari ahli media memperoleh presentase sebesar 100% dengan kriteria sangat layak, ahli materi memperoleh presentase sebesar 96% dengan kriteria sangat layak, dan praktisi memperoleh presentase sebesar 95% dengan kriteria sangat layak. Penelitian uji coba produk dilakukan dengan uji terbatas dan jumlah sampel sebanyak 6 orang siswa kelas VIII SMP Negeri 4 Tarakan. Hasil respons siswa yang diperoleh rata-rata sebesar 88% dengan kriteria siswa sangat tertarik terhadap lembar kerja siswa (LKS) yang dikembangkan. Dari hasil yang diperoleh lembar kerja siswa (LKS) yang berjudul “Sistem Pernapasan Manusia” sangat layak digunakan sebagai sumber belajar siswa.
Kata Kunci :Berpikir Kritis, LKS, Proyek, Sistem Pernapasan Manusia

The purpose of the research was to develop the students worksheets based on project to improve students' critical thinking skills on the material of the human respiratory system at SMPN 4 Tarakan which is feasible based on expert assessment and determine the students' responses to the students worksheets based on project to improve students' critical thinking skills on the material of the human respiratory system. The type of the research is research and development (R&D) with Borg & Gall model research design (1983). The steps of the Borg & Gall (1983) model used in this research are starting from research and initial data collection, planning, initial product development, initial product trials and product revision. Data analysis used descriptive qualitative and quantitative approaches. The results of the product development of the students worksheets obtained validation results from media experts got a percentage of 100% with very feasible criteria, material experts got a percentage of 96% with very feasible criteria, and practitioners got a percentage of 95% with very feasible criteria. The field trial of the product was conducted with a limited test and the number of samples was 6 students of class VIII SMPN 4 Tarakan. The results of the students' responses obtained averaged 88% with the students criteria are very interested in the developed students worksheets. Based on the results obtained, the students' worksheets entitled human respiratory system are very feasible to use as the student learning resource. Keywords: Students Worksheets, Project, Critical Thinking, Human Respiratory System