Trump (Donald Trump) and Kim Jong-un have met before, a total of three times.

June 12, 2018, Singapore Summit
This was their first meeting and also the first summit in history between a sitting U.S. president and a North Korean leader. The two held talks at the Capella Hotel on Sentosa Island in Singapore and signed a joint statement, promising to establish a new type of U.S.-North Korea relationship and achieve complete denuclearization of the Korean Peninsula.
February 27-28, 2019, Hanoi Summit
The second formal summit. Although no final agreement was reached on denuclearization measures and sanctions relief, the two sides engaged in in-depth discussions.
June 30, 2019, Panmunjom (DMZ) Meeting
The third brief meeting held at the Korean Demilitarized Zone (DMZ) in Panmunjom. Trump became the first sitting U.S. president to step onto North Korean territory (he crossed the military demarcation line by a few steps). Kim Jong-un invited him to enter the North Korean side, and they shook hands and had a brief conversation. Afterwards, they also held a trilateral meeting with South Korean President Moon Jae-in.