  We report the result of a search for neutrinos in coincidence with solar
flares from the GOES flare database. The search was performed on a 10.8
kton-year exposure of KamLAND collected from 2002 to 2019. This large exposure
allows us to explore previously unconstrained parameter space for solar flare
neutrinos. We found no statistical excess of neutrinos and established 90%
confidence level upper limits of $8.4 \times 10^7$ cm$^{-2}$ ($3.0 \times
10^{9}$ cm$^{-2}$) on electron anti-neutrino (electron neutrino) fluence at 20
MeV normalized to the X12 flare, assuming that the neutrino fluence is
proportional to the X-ray intensity.
