| Order: | Arima clan head |
| Predecessor: | Arima Haruzumi |
| Successor: | Arima Harunobu |
| Arima Yoshisada | |
| Native Name: | 有馬 義貞 |
| Birth Name: | Yoshinao |
| Birth Date: | Daiei 1 (1521) |
| Birth Place: | Hizen, Ashikaga, Japan |
| Death Date: | Tensho 5 (15 January 1577) |
| Nickname: | Don Andres (spiritual) |
| Occupation: | Tycoon |
| Known For: | Leader of Arima clan |
| Parents: | Arima Haruzumi (father), Ōmura Sumitomo daughter's (mother) |
| Relatives: | Ōmura Sumitada, Naokazu Chijiwa, Mori Matsuura, Sutra Shiki (siblings) |
Arima Yoshisada (Japanese: 有馬義貞) was a Japanese daimyo from Hizen. He lived during the Sengoku period. He was the son and successor of Arima Haruzumi and the father of Kirishitan daimyo Arima Harunobu.[1] [2] He was the 12th head of the Arima clan.[3]
In 1563, Yoshisada formed a partnership with the Portuguese and the Jesuits due to the goods they brought to the domain. In 1576, Yoshisada converted to Christianity, along with some of his subjects.[4] He was given the bapstimal name Don Andre.[5]