| Marina Znak | |
| Birth Date: | 17 May 1961 |
| Birth Place: | East Berlin, East Germany |
| Sport: | Rowing |
| Club: | Dynamo Minsk |
Marina Nikolayevna Znak-Sinelshchikova (be|Марина Николаевна Знак-Синельщикова; born 17 May 1961 in East Berlin, East Germany) is a Belarusian rower, who won a bronze medal at the 1996 Summer Olympics while representing Belarus. Before 1991, she competed internationally for the Soviet Union, winning two golds and a silver medal for the Soviets at the World Rowing Championships from 1985 to 1991. While appearing at the World Rowing Championships for Belarus from 1995 to 1999, she won a further two gold medals and a bronze.