Staff Sergeant Piotr Śmietański (born 27 June 1899 in Zawady village – died probably on 23 February 1950), was one of the main executioners in Stalinist Poland, employed by the communist secret police Urząd Bezpieczeństwa.

Śmietański was stationed at the Mokotów Prison in the Warsaw borough of Mokotów (Polish: Więzienie mokotowskie) known also as Rakowiecka Prison located at 37 Rakowiecka Street. From World War II until the collapse of the Eastern Bloc in 1989, Mokotów Prison – where Śmietański conducted his deeds – was a place of detention, torture and execution of the Polish anti-communist opposition.

Śmietański – nicknamed by the inmates as the "Butcher of the Mokotow Prison" – executed personally and supervised the executions of hundreds of opponents of the Stalinist regime in PRL. Among them were prominent politicians, social activists and Polish underground fighters, including Lieutenants Jerzy Miatkowski, Tadeusz Pelak, Edmund Tudruj, Arkadiusz Wasilewski, Roman Gronski, Capt. Stanislaw Lukasik, Comdt. Hieronim Dekutowski (killed by Śmietański in one day, on March 7, 1949), Adam Doboszyński (August 29), Major Zygmunt Szendzielarz, Lieutenants Henryk Borowski, Antoni Olechnowicz, Lucjan Minkiewicz (February 8, 1951), Capt. Stanisław Sojczyński, Lt. Antoni Wodyński from AK, and countless others, including victims of the notorious March 1, 1951 Mokotów Prison execution, who were given five consecutive death sentences each. Brig. General Emil August Fieldorf was hanged rather than shot to be humiliated.

The head of the Mokotów Prison, Alojzy Grabicki, was sometimes present at the executions. The victims' dead bodies – often undressed and placed in empty cement bags – were wheeled out at night and buried in unmarked graves, leveled out afterwards in the vicinity of different Warsaw cemeteries: in Służew (till mid 1948), the Mokotów and the Powązki cemeteries, or in open fields, in around Pola Mokotowskie, Kabacki forest and Okęcie.

On May 25, 1948, Śmietański personally executed Witold Pilecki, the founder of the Secret Polish Army and prominent member of the Armia Krajowa, famous for his daring mission to the Auschwitz concentration camp. Śmietański is believed to have been paid 1,000 Polish złoty for each execution he carried out, a substantial amount of money under Stalinism. According to Chodakiewicz, he emigrated from Poland in 1968, but other historians disagree. For instance, Siergiejczyk mentions a different Śmietański, named Józef, who also left Poland in 1968 as a result of the Polish anti-Zionist campaign conducted by the Polish United Workers' Party.

In 2003 the Institute of National Remembrance (IPN) launched an investigation in order to establish the whereabouts of Piotr Śmietański, with the intention of interviewing him about the remains of Pilecki. They found out that all personal data pertaining to Śmietański was earlier removed from official government records, including from archives of the Ministry of Defence, and the Prison Services. The investigation was halted in 2004. Historian Jacek Pawłowicz from IPN in his 2008 book about Pilecki claimed that Śmietański died of tuberculosis at the age of 50 in the year of his last known Mokotów executions.