The strong acid HCl (hydrochloric acid) and the strong base KOH (potassium hydroxide) produce potassium chloride.

The chemical reaction between HCl and KOH can be represented as follows:

$$HCl + KOH \rightarrow KCl + H2O$$

In this reaction, the hydrogen ion (H+) from HCl combines with the hydroxide ion (OH-) from KOH to form water (H2O), while the potassium ion (K+) from KOH and the chloride ion (Cl-) from HCl combine to form potassium chloride (KCl).