List of symphonies by key

This list of symphonies by key is a list of symphonies sorted by key. For the least often used keys in orchestral music, the symphony listed might be famous only for being in that key.
C major.
In the Classical period, C major was the key most often chosen for symphonies with trumpets and drums. Even in the Romantic period, with its greater use of minor keys and the ability to use trumpets and drums in any key, C major remained a very popular choice of key for a symphony. The following list only includes the most famous examples.
C minor.
The key of C minor was, like most other minor keys, associated with the literary Sturm und Drang movement during the Classical period. But ever since Ludwig van Beethoven's famous Symphony No. 5, Op. 67, of 1808, C minor imparts a symphony in the key a character of heroic struggle. Early classical symphonies in the key typically ended in C minor but with a picardy third for the very final chord. Following Beethoven's precedent, most C minor symphonies of the Romantic period end in C major. Another option is to end in E-flat major (the relative key), as Mahler does in his Second Symphony.
C-sharp minor.
Even by Mahler's time, symphonies in C-sharp minor were rare. Some of the works listed below might have no claim to fame besides being in this key.
D-flat major.
Symphonies in D-flat major are much rarer than those in C-sharp minor and one has to look beyond the standard core repertoire to find them.
D major.
Baroque and Classical symphonies in D major typically used horns in D (reading a seventh down) and when they used trumpets, trumpets in D reading a step up. The following list includes only the most famous of the Classical and Romantic periods.
D minor.
Baroque and Classical symphonies in D minor usually used 2 horns in F (whereas for most other minor keys 2 or 4 horns were used, half in the tonic and half in the relative major). Michael Haydn's Symphony No. 29 in D minor is notable for using two trumpets in D (the horns are in F but change to D for the coda of the finale). In the Romantic era, D minor symphonies, like symphonies in almost any other key, used horns in F and trumpets in B-flat.
E-flat minor.
The two examples of symphonies in E-flat minor that come up most readily are both Sixth Symphonies by Soviet composers.
E major.
In the classical period, symphonies in E major used horns in E but no trumpets. 
F minor.
Even in the Sturm und Drang era, F minor was not a frequent choice for a minor key symphony, though Haydn did contribute one.
F-sharp major.
The only notable (completed) symphony written explicitly in F-sharp major is Erich Wolfgang Korngold's Symphony in F-sharp major, Op. 40 of 1950.
Gustav Mahler's unfinished Tenth Symphony is in this key. So is Olivier Messiaen's "Turangalîla-Symphonie", as several of its movements including the finale are in that key, although it could be excluded on the grounds that it is very far from traditionally tonal.
F-sharp minor.
Though it has just three sharps and its relative major was used somewhat frequently, F-sharp minor was an unusual choice of key in the Classical era.
G major.
In the Baroque and Classical periods, G major was one of the most often used keys. Classical symphonies in G major typically had horns in G, but no trumpets. In the Romantic era, the key was less often used. The following list only includes the most famous works.
G minor.
G minor was a frequent choice for minor key symphonies. In the Classical period, symphonies in G minor almost always used four horns, two in G and two in B-flat alto.
A-flat major.
Although A-flat major was chosen often enough for inner movements of symphonies in other keys (most notably slow movements of C minor symphonies), there are very few symphonies with A-flat major as their main key.
G-sharp minor.
Because A-flat minor has seven flats in its key signature, composers usually use the enharmonic equivalent G-sharp minor, which only has five sharps. It is infrequent even in piano music, and even rarer in orchestral music in general.
A major.
The following list only includes the most famous A major symphonies.
B-flat major.
Haydn's Symphony No. 98 is credited as the first symphony written in B-flat major in which trumpet and timpani parts are included. Actually, his brother Michael Haydn had written one such symphony earlier, No. 36. However, Joseph still gets credit for writing the timpani part at actual pitch with an F major key signature (instead of transposing with a C major key signature), a procedure that made sense since he limited that instrument to the tonic and dominant pitches. Many editions of the work, however, use no key signature and specify the instrument as "Timpani in B-flat - F." (Note that in German, the pitch B-flat is called "B", and B natural is "H", thus the specification for timpani in a B-flat work could be written "Pauken in B. - F.")
B-flat minor.
B-flat minor occurs often enough in the piano repertoire, much less so in the orchestral repertoire. Even allowing little-known works, the list is rather short.
B major.
Haydn's use of B major in his Symphony No. 46 was deemed "extraordinary" for a symphony in the 18th century.
B minor.
B minor is the key of some famous symphonies in the repertoire, as well as a few lesser known ones.