Heat vegetable oil in a large skillet or wok over medium-high heat.
Add the onion and red bell pepper, sautéing for 5 minutes until vegetables begin to soften.
Add the garlic, ginger, and red curry paste; stir constantly for 1 minute until the mixture is fragrant.
Pour in the coconut milk, fish sauce, and brown sugar; whisk to combine and bring the liquid to a gentle simmer.
Add the shrimp to the skillet and cook for 3 to 4 minutes, turning once, until they are pink and opaque.
Remove the skillet from heat and stir in the lime juice and chopped cilantro before serving.