In IAST
o? bh?r bhuva? sva?
(a) tat savitur vare?ya?
(b) bhargo devasya dh?mahi
(c) dhiyo yo na? prachoday?t

In IAST Long Form
o? bh?r o? bhuva? o? sva? o? ma? o? jana? o? tapa? o? sat ya?
(a) o? tat savitur vare?ya?
(b) bhargo devasya dh?mahi
(c) dhiyo yo na? prachoday?t
[edit]Translation

Ralph T.H. Griffith (1896):
(a, b) "May we attain that excellent glory of Savitr the God:"
(c) "So may he stimulate our prayers."
Word-by-word explanation:-
om The mystical Om syllable.
bh? "earth"
bhuvas "atmosphere"
svar "light, heaven"
tat "that"
savitur devasya "of Savitr, the god" (genitives of savitr-, 'stimulator, rouser; name of a sun-deity' and deva- 'god' or 'demi-god')
varenyam accusative of varenya- "desirable, excellent"
bhargo "radiance, lustre, splendour, glory"
dh?mahi "may we attain" (1st person plural middle optative of dh?- 'set, bring, fix' etc.)
dhiya? na? "our prayers" (accusative plural of dhi- 'thought, meditation, devotion, prayer' and na? enclitic personal pronoun)
ya? pracoday?t "who may stimulate" (nominative singular of relative pronoun yad-; causative 3rd person of pra-cud- 'set in motion, drive on, urge, impel')

Other translations, circumlocutions and interpretations:

Valerie J. Roebuck (2003):
We meditate on the lovely
Glory of the god Savitr
That he may stimulate our minds

William Quan Judge [1]
"Unveil, O Thou who givest sustenance to the Universe, from whom all proceed, to whom all must return, that face of the True Sun now hidden by a vase of golden light, that we may see the truth and do our whole duty on our journey to thy sacred seat."
Kurma Purana, "freely translated" by Swami Vivekananda [2]
"'We meditate on the glory of that Being who has produced this universe; may He enlighten our minds.' Om is joined to it at the beginning and the end."

Gayatri Pariwar
"O God, Thou art the giver of life, the remover of pain and sorrow, the bestower of happiness; O Creator of the Universe, may we receive Thy supreme, sin destroying light; may Thou guide our intellect in the right direction."