Guldborgsund is the strait between the Danish islands of Lolland and Falster. It connects Smålandsfarvandet in the north with the Bay of Mecklenburg in the south. It is navigable for craft of up to 6 metres draught in its northern part and is used for commercial traffic to Nykøbing Falster. The southern part is much shallower with a minimum depth of approximately 2 metres, and can only be used by yachts and other small craft.
Guldborgsund is also the name of a minesweeper that served in the Royal Danish Navy from 1956-1993. It was built by Stephens Brothers Inc. in Stockton, USA, and launched March 14, 1956. Two 900 hp (670 kW) General Motorsdiesel engines powered it to a max speed of 13.5 knots (25 km/h). With 375 tons of displacement, it had a range of 3,600 nautical miles (6,670 km) at 7 knots (13 km/h). It was crewed by 33-37 men, including four officers, during its service. It was decommissioned on May 4, 1993.