Interactions between the MLCT excited states of Ru(bpy)3 2+ (bpy ) 2,2¢-bipyridine) or Ru(bpz)3 2+ (bpz ) 2,2¢-bipyrazine) and phenol or monochlorophenols have been investigated in aqueous solution using steadystate and time-resolved spectrofluorimetry. The presence of phenol (PhOH), which does not quench *Ru(bpy)3 2+ in mildly acidic solution, causes the emission to undergo a blue shift with increasing [PhOH]; the emission quantum yields and the excited-state lifetimes decrease with increasing [PhOH] at low temperatures (5-35 °C) but increase with increasing [PhOH] at higher temperatures (35-70 °C). This behavior is understood in terms of the variations in the rate constants of the temperature-independent radiative and nonradiative decays of *Ru(bpy)3 2+ and the activation-controlled population of the metal-centered excited state as [PhOH] is changed. The presence of chlorophenols has no effect on the photophysics of *Ru(bpy)3 2+; PhOH reductively quenches *Ru(bpz)3 2+.