Joachim Westphal (born at Hamburg 1510 or at the beginning of 1511; died there 16 January 1574) was a German "Gnesio-Lutheran" theologian and Protestant reformer.

He was educated in the school of the parish of St. Nicolai in his native city, then in Lüneburg, and entered the University of Wittenberg, where he became the pupil of Melanchthon and Luther.

In 1552 he published Farrago confusanearum et inter se dissidentium opinionum de coena Domini, ex Sacramentariorum libris congesta, a warning against those who deny the presence of Christ in the Lord's Supper.

Westphal replied to Calvin in Adversus cuiusdam sacramentarii falsam criminationem iusta defensio, in qua et eucharistiae causa agitur (1555), to which Calvin answered in Secunda defensio piae et orthodoxae de sacramentis fidei (1556), which was an attempt to draw to his side the Philippists of Saxony and Lower Germany.

[1] Other works of Westphal occasioned by this controversy are: Epistola Joachimi Westphali, qua breviter respondet ad convicia J. Calvini (1556); Confessio fidei de eucharistiae sacramento, in qua ministri ecclesiarum Saxoniae...astruunt corporis et sanguinis D. n. J. Christi praesentiam in coena sancta, et de libro Calvini ipsis dedicato respondent (Magdeburg, 1557); Justa defensio adversus insignia mendacia J. a Lasco, quae in epistola ad Poloniae regem contra Saxonicas ecclesias sparsit (1557); Apologetica scripta Johannis Westphali, quibus et sanam doctrinam de eucharistia defendit et foedissimas calumnias sacramentariorum diluit (1558); Confutatio aliquot enormium mendaciorum Johannis Calvini (1558); Apologia confessionis de Coena Domini (1558).