I am a peasant in rural China during the late imperial period. Who owns my land? Who do I pay taxes to?

It really depends.

In theory, the emperor owns all of the land. But, in practice, this claim was never really exercised (there were disgraced officials and other people who had their land seized under the Ming and Qing.)

To get to your question specifically: it again depends. If you were near the capital (Beijing), you would pay directly to the central government (and, depending on how bad corruption was, the rate would be either lower or higher - in reality, theoretically, the rate was equal for everyone.) As you move away from the capital city, the Emperor begins to rely on provincial officials appointed by the central government to administer policy in provinces. These provincial officials relied on the cooperation of local elites. The effectiveness of tax policy (and frankly, policy in general) depended on the relationship between provincial officials and local elites (who themselves were often times bureaucrats). So, you would pay money to some bureaucrat. How much you pay? Well that depends on the relationship between you, elites within your village/town/city and provincial officials. As well as the relationship between provincial officials and those "higher up the food chain", if you will.

Who owns your land? In many cases, peasants owned their own land. In other cases, peasants were landless and sold their labor to those who did own land. Then there were peasants would sometimes sell their land to landlords who would charge rent, during times of crisis of course.