A '''complexometric indicator''' is an [[ionochromism|ionochromic]] [[dye]] that undergoes a definite color change in presence of specific metal [[ion]]s.<ref name="isbn0-416-19290-4">{{cite book |author1=Flaschka, H. |author2=Schwarzenbach, G. |author3=Schwarzenbach, Gerold |title=Complexometric titrations |publisher=Methuen |___location=London |year=1969 |pages= |isbn=0-416-19290-4 |oclc= |doi= |accessdate=}}</ref> It forms a weak [[complex (chemistry)|complex]] with the ions present in the solution, which has a significantly different color from the form existing outside the complex.
Complexometric indicators are also known as pM indicators.<ref name="isbn1-898563-47-0">{{cite book |author=M. A. Malati |title=Experimental Inorganic/Physical Chemistry: An Investigative, Integrated Approach to Practical Project Work (Horwood Series in Chemical Science) |publisher=Albion/Horwood Pub |___location= |year=1999 |page=20 |isbn=1-898563-47-0 |oclc= |doi= |accessdate=}}</ref>
