NtRenameKey - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTREGAPI_H

/**
 * Renames a registry key.
 * 
 * @param[in] KeyHandle A handle to the key to be renamed.
 * @param[in] NewName A pointer to a UNICODE_STRING structure that specifies the new name of the key.
 * @return NTSTATUS Successful or errant status.
 */
NTSYSCALLAPI
NTSTATUS
NTAPI
NtRenameKey(
    _In_ HANDLE KeyHandle,
    _In_ PUNICODE_STRING NewName
    );

#endif

View code on GitHub
#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwRenameKey(
    _In_ HANDLE KeyHandle,
    _In_ PUNICODE_STRING NewName
    );

#endif

View code on GitHub

This function is documented in Windows SDK.