To whoever owns the whole revenue number, which is usually the CRO or the CEO. Reporting into sales alone tends to reduce RevOps to sales ops and starves marketing and CS work; reporting into finance tends to produce accurate reporting nobody in the field uses.
The structural test is whether RevOps can set definitions that bind all three revenue functions. If it can't, the reporting line is wrong regardless of the org chart's elegance. Structure, not headcount, is what makes the function effective.
Every claim above comes from work LeanScale published. These are the sources.