The USS Philolaus (NCC-3811) was a mk VI Ptolemy-class Federation class I transport tug starship ordered for Starfleet service in the 23rd century.

Construction of Philolaus was authorized by the Starfleet appropriation of stardate 0965. (TOS reference: Star Fleet Technical Manual)

The stardate given would seem to suggest this ship was ordered sometime before the TOS era. It is not even known if this vessel was built, only that it was authorized.

Ptolemy-class starships
Ptolemy-subclass	Al Rashid • Anaxagoras • Anaximander • Aristarchus • Copernicus • Eratosthenes • Galilei • Hevelius • Hipparchus • Ibn Daud • Masada • Philolaus • Ptolemy • Pythagoras • Thales • Ulugh Beg
Keppler-subclass	Ambartsumian • Brahe • Cassini • Deslandres • Donati • Flamarion • Keppler • Kidinnu • Leverrier • Luyten • Messier • Newton • Piazzi • Riccioli • Schiaparelli
Doppler-subclass	Airy • Apian • Baade • Bayer • Biela • Bondi • Brouwer • Campell • Carrington • Chamberlain • Chauvenet • Clark • Columbo • Dollfus • Doppler • Dreyer • Eddington • Encke • Fracastor • Galle • Gaillot • Gautier • Goldricke • Hale • Halley • Hayashi • Hencke • Herschell • Hirayami • Holden • Hubbard • Hubble • Humanson • Jansky • Jeffrey • Kaula • Klepstra • Kruger • Kuiper • Laplace • Leavitt • Lockyer • Mitchell • Newcomb • Oort • Palitzsch • Peale • Pickering • Popper • Pritchett • Reber • Rittenhouse • Ross • Sabine • Schmidt • Tombaugh • Toscanelli • Van De Kamp • Vogel • Von Zach • Walker • Wolaston • Wright
Dollond-subclass	Adams • Baum • Bessel • Bode • Carpenter • Challis • Chandrasekher • Delambre • Dollond • Eichelberger • Flamsteed • Frost • Gold • Goldreich • Hall • Henderson • Hertzsprung • Hoyle • Huggins • Irwin • Jeans • Kohlschutter • Lagrange • Lowell • Langley • Moulton • Olbers • Pierce • Plaskett • Pogson • Roques • Russell • Sandage • Schwabe • Shapley • Slipher • Savary • Scheiner • Secchi • Shklovsky • Struve • Swift • Todd • Van de Hulst • Van Maanen • Wolf • Young