This article presents the development of graphene-based in-plane micro-supercapacitors with high power and energy densities. The micro-supercapacitors are fabricated on arbitrary substrates using micropatterning of graphene films with a nanoscale thickness of 6–100 nm. The resulting devices deliver an area capacitance of 80.7 μF cm⁻² and a stack capacitance of 17.9 F cm⁻³. They exhibit a power density of 495 W cm⁻³, which is higher than that of electrolytic capacitors, and an energy density of 2.5 mWh cm⁻³, comparable to lithium thin-film batteries. The devices also show superior cycling stability, retaining over 98.3% of their capacitance after 100,000 cycles. These microdevices can operate at ultrahigh rates up to 1,000 V s⁻¹, three orders of magnitude higher than conventional supercapacitors. The in-plane geometry allows for rapid ion transport along the planar graphene sheets, enabling high power and energy densities. The micro-supercapacitors are fabricated using a combination of graphene oxide reduction, lithography, and electrochemical polymerization. The devices are tested on both rigid and flexible substrates, demonstrating excellent performance and flexibility. The results show that the in-plane geometry significantly enhances the electrochemical performance of the micro-supercapacitors, with the MPG-MSCs outperforming other types of micro-supercapacitors in terms of power and energy density. The study highlights the potential of graphene-based micro-supercapacitors for various miniaturized or flexible electronic applications.This article presents the development of graphene-based in-plane micro-supercapacitors with high power and energy densities. The micro-supercapacitors are fabricated on arbitrary substrates using micropatterning of graphene films with a nanoscale thickness of 6–100 nm. The resulting devices deliver an area capacitance of 80.7 μF cm⁻² and a stack capacitance of 17.9 F cm⁻³. They exhibit a power density of 495 W cm⁻³, which is higher than that of electrolytic capacitors, and an energy density of 2.5 mWh cm⁻³, comparable to lithium thin-film batteries. The devices also show superior cycling stability, retaining over 98.3% of their capacitance after 100,000 cycles. These microdevices can operate at ultrahigh rates up to 1,000 V s⁻¹, three orders of magnitude higher than conventional supercapacitors. The in-plane geometry allows for rapid ion transport along the planar graphene sheets, enabling high power and energy densities. The micro-supercapacitors are fabricated using a combination of graphene oxide reduction, lithography, and electrochemical polymerization. The devices are tested on both rigid and flexible substrates, demonstrating excellent performance and flexibility. The results show that the in-plane geometry significantly enhances the electrochemical performance of the micro-supercapacitors, with the MPG-MSCs outperforming other types of micro-supercapacitors in terms of power and energy density. The study highlights the potential of graphene-based micro-supercapacitors for various miniaturized or flexible electronic applications.