  We report the first blazar detection by the AGILE satellite. AGILE detected
3C 454.3 during a period of strongly enhanced optical emission in July 2007.
AGILE observed the source with a dedicated repointing during the period 2007
July 24-30 with its two co-aligned imagers, the Gamma-Ray Imaging Detector and
the hard X-ray imager Super-AGILE sensitive in the 30 MeV-50 GeV and 18-60 keV,
respectively. Over the entire period, AGILE detected gamma-ray emission from 3C
454.3 at a significance level of 13.8-$\sigma$ with an average flux (E$>$100
MeV) of $(280 \pm 40) \times 10^{-8}$ photons cm$^{-2}$ s$^{-1}$. The gamma-ray
flux appears to be variable towards the end of the observation. No emission was
detected by Super-AGILE in the energy range 20-60 keV, with a 3-$\sigma$ upper
limit of $2.3 \times 10^{-3}$ photons cm$^{-2}$ s$^{-1}$. The gamma-ray flux
level of 3C 454.3 detected by AGILE is the highest ever detected for this
quasar and among the most intense gamma-ray fluxes ever detected from Flat
Spectrum Radio Quasars.
