Stēamtrǣg (Niwenglisc: steam locomotive) is sēo hātweorðe trǣg. Hīe wæs gelōme brūcod betwēonan þæs geāres 1830 and 1970. Æfter þǣm wearþ oft brūcod dēosol and ǣlenge rēawegtrǣgas. Sēo ǣrest stēamtrǣg wearþ geworht fram Rīċardes Trevithick for an trǣgbricg brūcod for bewegen irne at Ān Isernweorc on Wealas. Sēo stēamtrǣg wirceaþ bī bǣninga ane fȳliscas swā swā col on ān gehātendum stōwe ġenemned fȳrboc. Þæt ālīeþ hāte gās þe stīgeþ and fēraþ þurh tūban in ān cōlþēorf - ān bīg spacu mid wæter on. Þis hīetþ þæt wæter, wyrcende hātne stēam. Sēo stēam is þonne genumen þurh ǣnne ōþerne tūban tō ānum cyllindra. Sēo stēam þonne byreþ þone bǣþ, sēo eft byreþ ān iren rōd þe is getenge tō þǣm hƿēolcum, wyrcende þone stēamtrǣg tō scūfan. Sēo stēam þonne stīgeþ ūt þurh þone wēoh.
Stēamtrǣgas sind tō dæġe brūcade on manigum gestigendan landum þǣr þā rēawegas nǣron ārǣrede mid ǣlenge.