The stage of mitosis where chromosomes are most tightly condensed is metaphase.

Here's why:

* Prophase: Chromosomes begin to condense, but they are still relatively loose.

* Metaphase: The chromosomes are fully condensed and lined up along the metaphase plate (the center of the cell). This tight condensation allows for proper separation of the chromosomes during anaphase.

* Anaphase: The sister chromatids of each chromosome are pulled apart, but they remain condensed until telophase.

* Telophase: The chromosomes start to uncoil and become less condensed as the nuclear envelope reforms.

So, metaphase is the stage where the chromosomes are at their most compact and tightly packed.