Graphene-based optoelectronic devices have recently attracted much attention for the next-generation electronic-photonic integrated circuits. However, it remains elusive whether it is feasible to create graphene-based lasers at the chip scale, hindering the realization of such a disruptive technology. In this work, we theoretically propose that Landau-quantized graphene enabled by strain-induced pseudomagnetic field can become an excellent gain medium that supports lasing action without requiring an external magnetic field. Tight-binding theory is employed for calculating electronic states in highly strained graphene while analytical and numerical analyses based on many-particle Hamiltonian allow studying detailed microscopic mechanisms of zero-field graphene Landau level laser dynamics. Our proposed laser presents unique features including a convenient, wide-range tuning of output laser frequency enabled by changing the level of strain in graphene gain media. The chip-scale graphene laser may open new possibilities for graphene-based electronic-photonic integrated circuits.