Rinder­kennzeichnungs- und Rindfleisch­etikettierungs­überwachungs­aufgaben­übertragungs­gesetz (listen; RkReÜAÜG; literally, "Cattle marking and beef labeling supervision duties delegation law") was a law of the German state of Mecklenburg-Vorpommern of 1999, repealed in 2013. It dealt with the supervision of the labeling of beef after an outbreak of mad cow disease.

The name of the law is a famous example of the virtually unlimited compounding of nouns that is possible in many Germanic languages. German orthography uses "closed" compounds, concatenating nouns to form one long word. This is unlike most English compounds, which are separated using spaces or hyphens.

Strictly speaking, it is made up of two words, because a hyphen at the end of a word is used to show that the word will end in the same way as the following. Consequently, the two words would be Rinder­kennzeichnungs­überwachungs­aufgaben­übertragungs­gesetz and Rindfleisch­etikettierungs­überwachungs­aufgaben­übertragungs­gesetz, coming in at 58 and 63 letters, respectively.

This is the official short title of the law; its full name is Gesetz zur Übertragung der Aufgaben für die Überwachung der Rinderkennzeichnung und Rindfleischetikettierung, corresponding to Law on delegation of duties for supervision of cattle marking and beef labeling. Most German laws have a short title consisting of a composite noun.

Words this long are not very common in German. When the law was proposed in the state parliament, the members reacted with laughter and the responsible minister Till Backhaus apologized for the "possibly excessive length". In 1999, the Association for the German Language nominated Rindfleisch­etikettierungs­überwachungs­aufgaben­übertragungs­gesetz for its Word of the Year award, but it lost to das Millennium, a Latin word that gained in usage at the time, complementing the German word for millennium, Jahrtausend.

In 2003, a decree was established that modified some real estate-related regulations; its name was longer than the above law: Grundstücks­verkehrs­genehmigungs­zuständigkeits­übertragungs­verordnung (long title: Verordnung zur Übertragung der Zuständigkeiten des Oberfinanzpräsidenten der Oberfinanzdirektion Berlin nach § 8 Satz 2 der Grundstücksverkehrsordnung auf das Bundesamt zur Regelung offener Vermögensfragen, GrundVZÜV), roughly Regulation on the delegation of authority concerning land conveyance permissions. At 67 letters, it surpassed the RkReÜAÜG, but was repealed in 2007.

• German compounds
• Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu
• Donau­dampfschiffahrts­elektrizitäten­haupt­betriebswerkbau­unterbeamten­gesellschaft
• Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch
• Longest word in English
• Scriptio continua

• Gesetzestext (full text of the law) at the Wayback Machine (archived June 18, 2012) (in German)
• Official parliamentary record of the debate (pdf, in German)
• A choir singing the word.