Szlama Ber Winer, nom de guerre Yakov (Ya'akov) Grojanowski (23 September 1911 – c. 10 April 1942), was a Polish Jew from Izbica Kujawska, who escaped from the Chełmno extermination camp during the Holocaust in German-occupied Poland.

Szlama Ber Winer escaped from the Waldlager work commando at Chełmno (German: Kulmhof), and described in writing the atrocities he witnessed at that extermination camp, not long before his own subsequent murder at the age of 30, in the gas chambers of Bełżec.

[2] Szlama Ber (Szlamek) was born in Izbica Kujawska near Koło on 23 September 1911 (or the 10th, in Julian calendar) to a Jewish merchant Iccak Wolf Winer (35 years of age) and Srenca née Laskow, his lawful wife according to the birth certificate from the Office of Public Records.

[10][11][12] Wanted by the Gestapo, Szlama Ber Winer was whisked to Zamość where subsequently he also wrote back to his friends at the Warsaw Ghetto about the existence of a death camp in Bełżec a mere 44 kilometres (27 mi) south of the city.

[10] A few days after writing this last communiqué, around the 10th of April 1942, he was apprehended together with members of his extended family, and deported to the Bełżec extermination camp along with some 3,000 Jews of the Zamość Ghetto, marched from the market place to the awaiting Holocaust trains at the station.

[11][13][14] Two weeks later, the 14-year-old nephew of Szlama Winer, Abram Bajler, wrote a postcard from Zamość to Warsaw – sent on 24 April 1942 – after the deportation of his own uncle to the death camp.