For cataloguing purposes, pieces by Ludwig van Beethoven are indentified in four ways:

• by opus number. These were assigned by his publishers, and follow the order in which his works were published, rather than the order they were written. This is why, for example, the Wind Octet of 1792 can be Opus 103, when Opus 102 and Opus 104 were written in 1815 and 1817 respectively. Everything up to Opus 135 inclusive was published in Beethoven's lifetime; later numbers were published posthumously.
• by WoO (Werke ohne Opuszahl - literally, "works without opus number") number. These were assigned by Georg Kinsky and Hans Halm (who took over from Kinsky after his death) in their 1955 catalogue of Beethoven's works.
• by AnH number - these are works listed in the appendix (German: Anhang, hence the abbreviation) of Kinsky's catalogue as being probably spurious. Some of these have since been shown to be authored by Beethoven.
• by Hess (abbreviated to H) number. These were assigned by Willy Hess in a listing published shortly after Kinsky's which includes pieces not included in the 19th century Complete Edition published by Breitkopf and Haertel. Hess includes many more fragmentary works than does Kinsky. Many pieces have both WoO and H numbers - in these cases, WoO numbers are generally favoured over Hess numbers.

There is also the Biamonti catalogue, compiled by Giovanni Biamonti and published in 1968. This combines the pieces with opus numbers and all the works from Kinsky's and Hess' catalogue with hitherto uncatalogued fragments to make a single chronological listing. Biamonti numbers are not very often referred to, however.

Most of Beethoven's best-known pieces have opus numbers, but there are exceptions, one of the most notable being "Für Elise", WoO 59.

Works with opus numbers

• Opus 1 (1795): Piano Trio No. 1 in E flat major, Piano Trio No. 2 in G major, Piano Trio No. 3 in C minor.
• Opus 2 (1796): Piano Sonata No. 1 in F minor, Piano Sonata No. 2 in A major, Piano Sonata No. 3 in C major.
• Opus 3 (1794): String Trio No. 1 in E flat major.
• Opus 4 (1795): String Quintet in E flat major.
• Opus 5 (1796): Sonata for Piano and Cello No. 1 in F major, Sonata for Piano and Cello No. 2 in G minor.
• Opus 6 (1797): Piano Sonata for four hands.
• Opus 7 (1797): Piano Sonata No. 4 in E flat major.
• Opus 8 (1797): Serenade in D major for string trio.
• Opus 9 (1798): String Trio No. 2 in G major, String Trio No. 3 in D major, String Trio No. 4 in C minor.
• Opus 10 (1798): Piano Sonata No. 5 in C minor, Piano Sonata No. 6 in F major, Piano Sonata No. 7 in D major.
• Opus 11 (1798): Piano Trio No. 4 in B flat major.
• Opus 12 (1798): Violin Sonata No. 1 in D major, Violin Sonata No. 2 in A major, Violin Sonata No. 3 in E flat major.
• Opus 13 (1799): Piano Sonata No. 8 in C minor "Pathetique."
• Opus 14 (1799): Piano Sonata No. 9 in E major, Piano Sonata No. 10
• Opus 15: Piano Concerto No. 1 in C major.
• Opus 16 (1796): Quintet for Piano and Wind.
• Opus 17 (1800): Horn Sonata in F major.
• Opus 18 (1800): String Quartet No. 1 in F major, String Quartet No. 2 in G major, String Quartet No. 3 in D major, String Quartet No. 4 in C minor, String Quartet No. 5 in A major, String Quartet No. 6 in B flat major.
• Opus 19 (1795): Piano Concerto No. 2 in B flat major.
• Opus 20 (1799): Septet in E flat major.
• Opus 21 (1800): Symphony No. 1 in C major.
• Opus 22 (1800): Piano Sonata No. 11 in B flat major.
• Opus 23 (1801): Violin Sonata No. 4 in A minor.
• Opus 24 (1801): Violin Sonata No. 5 in F major "Spring."
• Opus 25 (1801): Serenade in D major for Flute, Violin and Viola.
• Opus 26 (1801): Piano Sonata No. 12 in A flat major.
• Opus 27 (1801): Piano Sonata No. 13 in E flat major, Piano Sonata No. 14 in C sharp minor "Moonlight."
• Opus 28 (1801): Piano Sonata No. 15 in D major.
• Opus 29 (1801): String Quintet in C major.
• Opus 30 (1803): Violin Sonata No. 6 in A major, Violin Sonata No. 7 in C minor, Violin Sonata No. 8 in G major.
• Opus 31 (1802): Piano Sonata No. 16 in G major, Piano Sonata No. 17 in D minor "Tempest," Piano Sonata No. 18 in E flat major.
• Opus 32 (1805): Song - An die Hoffnung.
• Opus 33 (1802): Seven Bagatelles for piano.
• Opus 34 (1802): Six variations for piano on an original theme, F major.
• Opus 35 (1802): Fifteen variations and a fugue for piano on an original theme, E flat major "Eroica."
• Opus 36 (1803): Symphony No. 2 in D major.
• Opus 37 (1803): Piano Concerto No. 3 in C minor.
• Opus 38 (1803): Piano Trio No. 8 (Arrangement of the Septet (Opus 20)).
• Opus 39 (1789): Two Preludes through all twelve major keys for piano.
• Opus 40 (1802): Romance for Violin in G major.
• Opus 41 (1803): Serenade for Paino and Flute or Violin in D major.
• Opus 42 (1803): Notturno for Viola and Piano in D major.
• Opus 43 (1801): The Creatures of Prometheus, Overture and Ballet music.
• Opus 44 (1792): Piano Trio No. 10 (Variations on an original theme in E flat major).
• Opus 45 (1803): 3 Marches for Piano, 4 hands.
• Opus 46 (1795): Song - Adelaide.
• Opus 47 (1802): Violin Sonata No. 9 in A major "Kreutzer."
• Opus 48 (1802): Songs - Bitten, Die Liebe des Nächsten, Vom Tode, Die Ehre Gottes aus der Natur, Gottes Macht und Vorsehung, Bußlied.
• Opus 49 (1792): Piano Sonata No. 19 in G minor, Piano Sonata No. 20 in G major.
• Opus 50 (1798): Romance for Violin in F major.
• Opus 51 (1797): Rondo in C major for piano, Rondo in G major for piano.
• Opus 52 (1805): Songs - Urians Reise um die Welt, Feuerfab, Das Liedchen von der Ruhe, Maigesang, Mollys Abschied, Die Liebe, Marmotte, Das Blümchen Wunderhold.
• Opus 53 (1803): Piano Sonata No. 21 in C major "Waldstein."
• Opus 54 (1804): Piano Sonata No. 22 in F major.
• Opus 55 (1805): Symphony No. 3 in E flat major "Eroica."
• Opus 56 (1805): Triple Concerto in C major.
• Opus 57 (1805): Piano Sonata No. 23 in F minor "Appassionata."
• Opus 58 (1807): Piano Concerto No. 4 in G major.
• Opus 59 (1806): String Quartet No. 7 in F major, String Quartet No. 8 in E minor, String Quartet No. 9 in C major, the Rasumovsky quartets
• Opus 60 (1807): Symphony No. 4 in B flat major.
• Opus 61 (1808): Concerto for Violin and Orchestra in D major.
• Opus 62 (1807): Overture - Coriolan.
• Opus 63 (1806): Arrangement of String Quintet (Opus 4): for Piano Trio.
• Opus 64 (1807): Arrangement of Piano Trio (Opus 3): for Piano and Cello.
• Opus 65 (1796): Aria - Ah perfido!
• Opus 66 (1796): Variations for Cello on Mozart's Ein Mädchen oder Weibchen.
• Opus 67 (1808): Symphony No. 5 in C minor.
• Opus 68 (1808): Symphony No. 6 in F major "Pastoral."
• Opus 69 (1808): Sonata for Piano and Violincello No. 3 in A major.
• Opus 70 (1808): Piano Trio No. 5 in D major "Ghost," Piano Trio No. 6 in E flat major.
• Opus 71 (1796): Wind sextet in E flat.
• Opus 72a (1805): Opera - Leonore (with Leonore No. 2 Overture)
• Opus 72b (1806): Opera - Leonore (with Leonore No. 3 Overture)
• Opus 72c (1814): Opera - Fidelio.
• Opus 73 (1809): Piano Concerto No. 5 in E flat major "Emperor."
• Opus 74 (1809): String Quartet No. 10 in E flat major "Harp."
• Opus 75 (1809): Songs - Mignon, Neue Liebe neues Leben, Aus Goethes Faust Es war einmal ein König, Gretels Warnung, An die fernen Geliebten, Der Zufriedene.
• Opus 76 (1809): Six variations for piano on an original theme, D major.
• Opus 77 (1809): Piano Fantasia.
• Opus 78 (1809): Piano Sonata No. 24 in F sharp major.
• Opus 79 (1809): Piano Sonata No. 25 in G major.
• Opus 80 (1808): Choral Fantasia.
• Opus 81a (1809): Piano Sonata No. 26 in E flat major "Les Adieux."
• Opus 81b (1795): Sextet in E flat.
• Opus 82 (1809): Songs - Hoffnung, Liebes-Klage, L'amante impatiente, L'amante impatiente, Lebens-Genuß.
• Opus 83 (1810): Songs - Wonne der Wehmut, Sehnsucht, Mit einem gemalten Band.
• Opus 84 (1810): Egmont (Overture and Incidental Music).
• Opus 85 (1804): Christ on the Mount of Olives
• Opus 86 (1807): Mass in C major.
• Opus 87 (1795): Trio for two Oboes and English Horn in C major.
• Opus 88 (1803): Song - Das Gluck der Freundschaft.
• Opus 89 (1814): Polonaise in C major.
• Opus 90 (1814): Piano Sonata No. 27 in E minor.
• Opus 91 (1813): Wellington's Victory ("Battle" Symphony).
• Opus 92 (1813): Symphony No. 7 in A major.
• Opus 93 (1814): Symphony No. 8 in F major.
• Opus 94 (1815): Song - An die Hoffnung.
• Opus 95 (1810): String Quartet No. 11 in F minor "Serioso."
• Opus 96 (1812): Violin Sonata No. 10 in G major.
• Opus 97 (1811): Piano Trio No. 7 in B flat major "Archduke."
• Opus 98 (1816): Song Cycle - An die ferne Geliebte.
• Opus 99 (1816): Song - Der Mann von Wort.
• Opus 100 (1814): Song - Merkenstein.
• Opus 101 (1816): Piano Sonata No. 28 in A major.
• Opus 102 (1815): Sonata for Piano and Cello No. 4 in C major, Sonata for Piano and Cello No. 5 in D minor.
• Opus 103 (1792): Wind octet in E flat.
• Opus 104 (1817): String Quintet (arrangement of Piano Trio No. 3).
• Opus 105 (1819): Six sets of variations for Piano and Flute.
• Opus 106 (1818): Piano Sonata No. 29 in B flat major "Hammerklavier."
• Opus 107 (1820): Ten sets of variations for Piano and Flute.
• Opus 108 (1818): Twenty-Five Scottish Songs.
• Opus 109 (1822): Piano Sonata No. 30 in E major.
• Opus 110 (1822): Piano Sonata No. 31 in A flat major.
• Opus 111 (1822): Piano Sonata No. 32 in C minor.
• Opus 112 (1815): Meeresstille und glückliche Fahrt (for chorus and orchestra).
• Opus 113 (1811): Singspiel - Die Ruinen von Athen (The ruins of Athens).
• Opus 114 (1822): March and Chorus - Die Weihe des Hauses.
• Opus 115 (1815): Overture - Zur Namensfeier.
• Opus 116 (1802): Vocal Trio with Orchestra - Tramte, empi tremate.
• Opus 117 (1811): Singspiel - King Stephen.
• Opus 118 (1814): Eligischer Gesang (for chorus and orchestra).
• Opus 119 (1822): Eleven new Bagatelles for piano.
• Opus 120 (1823): Thirty-three variations for piano on a waltz by Diabelli, C major (Diabelli Variations).
• Opus 121a (1803): Piano Trio No. 11 (Variations on Ich bin der Schneider Kakadu).
• Opus 121b (1822): Opferlied (for chorus and orchestra).
• Opus 122 (1824): Bundeslied (for chorus and orchestra).
• Opus 123 (1822): Mass in D major (Missa Solemnis).
• Opus 124 (1822): Overture - Die Weihe des Hauses (Consecration of the House).
• Opus 125 (1824): Symphony No. 9 in D minor "Choral."
• Opus 126 (1824): Six Bagatelles for piano.
• Opus 127 (1825): String Quartet No. 12 in E flat major.
• Opus 128 (1822): Song - Der Kuss.
• Opus 129 (1795): Rondo Capriccio for piano in G major (Rage over a lost penny).
• Opus 130 (1825): String Quartet No. 13 in B flat major.
• Opus 131 (1826): String Quartet No. 14 in C sharp minor.
• Opus 132 (1825): String Quartet No. 15 in A minor.
• Opus 133 (1826): Große Fuge in B flat major.
• Opus 134 (1826): Piano arrangement (4 hands) of Große Fuge.
• Opus 135 (1826): String Quartet No. 16 in F major.
• Opus 136 (1814): Cantata - Der glorreiche Augenblick.
• Opus 137 (1817): String Quintet (fugue): in D major.
• Opus 138 (1807): Overture - Leonore 1.

Werke ohne Opuszahl (incomplete)

• WoO 63 : Nine variations for piano on a march by Ernst Christoph Dressler
• WoO 64 : Six variations for piano or harp on a Swiss song
• WoO 65 : Twenty-four variations for piano on Vincenzio Righini's aria "Venni Amore"
• WoO 66 : Thirteen variations for piano on the aria "Es war einmal ein alter Mann" from Carl Ditters von Dittersdorf's opera Das rote Kappchen
• WoO 67 : Eight variations for piano four hands on a theme by Count Waldstein
• WoO 68 : Twelve variations for piano on the "Menuet a la Vigano" from Jakob Haibel's ballet La nozza disturbate
• WoO 69 : None variations for piano on "Quant'e piu bello" from Giovanni Paisiello's opera La Molinara
• WoO 70 : Six variations for piano on "Nel cor piu non mi sento" from Giovanni Paisiello's opera La Molinara
• WoO 71 : Twelve variations for piano on the Russian dance from Paul Wranitzky's ballet Das Waldmadchen
• WoO 72 : Eight variations for piano on "Mich brennt ein heifes Firber" from André-Ernest-Modeste Grétry's opera Richard Lowenherz
• WoO 73 : Ten variations for piano on "La stessa, la stessissima" from Antonio Salieri's opera Falstaff
• WoO 74 : "Ich denke dein" - song with six variations for piano four hands
• WoO 75 : Seven variations for piano on "Kind, willst du ruhig schlafen" from Peter Winter's opera Das unterbrochene Opferfest
• WoO 76 : Eight variations for piano on "Tandeln und scherzen" from Franz Xaver Sussmayr's opera Soliman II
• WoO 77 : Six easy variations for piano on an original theme
• WoO 78 : Seven variations for piano on "God Save the King"
• WoO 79 : Five variations for piano on "Rule Britannia"
• WoO 80 : Thirty-two variations in C minor on an original theme