Step 1: Understanding the terms.
- Aristocracy: Government by the nobility or elite class.
- Plutocracy: Government by the wealthy or rich people.
- Bureaucracy: Government by officials and administrative departments.
- Autocracy: Government by a single person with absolute power.
Step 2: Apply to the given question.
Since the question specifically asks for “government by the rich,” the correct term is plutocracy. Final Answer:
\[
\boxed{\text{Plutocracy}}
\]