This study presents a gate-tunable transmon qubit (gatemon) fabricated in planar germanium (Ge). The qubit is based on a semiconductor Josephson junction and is integrated into an Xmon circuit, with capacitively coupled transmission line resonator. The qubit frequency is tunable over a range of ~5 GHz, showing a quasimonotonic, linear dependence on gate voltage. The qubit relaxation time $ T_1 $ varies from ~80 ns to ~20 ns with gate voltage, while $ T_2^* $ does not show a clear trend. A control qubit on the same material stack shows a $ T_1 $ about five times longer than the semiconductor junction and $ T_2^* $ approaching $ 2T_1 $. The device demonstrates broadband tunability and quasi-linear frequency dispersion, making it a promising element for Andreev spin qubits (ASQs) and superconducting circuits requiring tunable elements. The qubit relaxation and coherence times are characterized, revealing possible limitations and areas for improvement. The study highlights the potential of Ge as a platform for hybrid qubits, with the possibility of integrating gatemons into ASQ circuits to allow in-situ frequency tuning and capacitive coupling to resonators. Future challenges include addressing issues introduced by shallow quantum wells and improving the microwave properties of the substrates. The results demonstrate the feasibility of a gate-tunable superconductor-semiconductor qubit on planar Ge, with potential applications in hybrid quantum circuits.This study presents a gate-tunable transmon qubit (gatemon) fabricated in planar germanium (Ge). The qubit is based on a semiconductor Josephson junction and is integrated into an Xmon circuit, with capacitively coupled transmission line resonator. The qubit frequency is tunable over a range of ~5 GHz, showing a quasimonotonic, linear dependence on gate voltage. The qubit relaxation time $ T_1 $ varies from ~80 ns to ~20 ns with gate voltage, while $ T_2^* $ does not show a clear trend. A control qubit on the same material stack shows a $ T_1 $ about five times longer than the semiconductor junction and $ T_2^* $ approaching $ 2T_1 $. The device demonstrates broadband tunability and quasi-linear frequency dispersion, making it a promising element for Andreev spin qubits (ASQs) and superconducting circuits requiring tunable elements. The qubit relaxation and coherence times are characterized, revealing possible limitations and areas for improvement. The study highlights the potential of Ge as a platform for hybrid qubits, with the possibility of integrating gatemons into ASQ circuits to allow in-situ frequency tuning and capacitive coupling to resonators. Future challenges include addressing issues introduced by shallow quantum wells and improving the microwave properties of the substrates. The results demonstrate the feasibility of a gate-tunable superconductor-semiconductor qubit on planar Ge, with potential applications in hybrid quantum circuits.