My upstairs neighbors are incredibly loud every night and it's driving me crazy?

Inter-floor noise (층간소음) is one of the most common and frustrating issues in Korean apartments, and there is an established process for it. Since you have already talked to them with no result, the recommended next step is not to keep going up yourself, because repeated direct confrontation is a leading cause of these disputes escalating badly. Instead, go through your building's management office (관리사무소); mediating noise complaints is part of their job, and a notice from them carries more weight and keeps you out of a personal conflict.

If that does not work, Korea has a dedicated national service, the Floor Noise Neighbor Center (층간소음 이웃사이센터) run by the Korea Environment Corporation, reachable at 1661-2642, which offers free phone counseling, mediation between neighbors, and even on-site noise measurement to check whether it exceeds the standards. There are official limits (roughly 39 to 43 decibels depending on day or night for continuous noise), and their measurement can support a formal complaint. For genuinely severe or late-night disturbances you can call the police at 112, though for ordinary noise they usually just ask the neighbor to quiet down. As a longer path there is mediation through the Environmental Dispute Resolution Commission and, in extreme cases, civil claims, but most situations resolve earlier. Document the noise with dates, times, and recordings, since that record supports every later step, and leaning on the management office and 1661-2642 rather than direct confrontation is the safest, most effective route.