| Keyword | Type | See | See also | Notes |
|---|---|---|---|---|
| X chromosome | Keyword | |||
| X-linked genetic disorders | Keyword | |||
| X-linked immunodeficiency | Keyword | |||
| X-ray analysis | Keyword | |||
| X-ray diffraction | Keyword | |||
| X-ray fluorescence | Keyword | |||
| X-rays | Keyword | |||
| Xaida | Ethnic group | Haida | ||
| Xavante | Ethnic group | Akwe Shavante | ||
| Xcalumkin site | Place | |||
| Xcaret site | Place | |||
| Xenophobia | Keyword | |||
| Xerente | Ethnic group | Sherente | ||
| Xeroderma pigmentosum | Keyword | |||
| Xhosa | Ethnic group | |||
| Xhosa language | Keyword | |||
| Xia dynasty | Keyword | |||
| Xianbei culture | Keyword | |||
| Xibe | Ethnic group | |||
| Xifan | Ethnic group | Pumi | ||
| Xikrin | Ethnic group | |||
| Xingu river region | Place | |||
| Xinjiang | Place | Sinkiang | ||
| Xiong-nu | Ethnic group | Hsiung-Nu | ||
| Xiongnu | Ethnic group | Hsiung-Nu | ||
| Xisha Paracel | Place | South China Sea Islands | ||
| Xishuangbanna | Place | China | ||
| Xituanshan culture | Keyword | |||
| Xochicalco site | Place | |||
| Xokleng | Ethnic group | Shokleng |