在正常大氣壓下哪種物質的熔點最高﹖

等一等，問題是問物質；並非單指是原素。
所以，應該是淘瓷、瓦片之類的東西。

已知熔点最高的物质是铪合金（Ta4HfC5)，熔点高达4215℃。
单质中熔点最高的
金属是钨，达到3410℃；
非金属是碳（石墨，金刚石略低，3550℃）3850℃

Perhapse this question is not essential for either daily life or scientific research.
In daily life, many materials can withstand temperature that we can access.
In scientific research, we are uneccessary to use such materials to make equipment to access extreme heat since many remote access methods help us do our job.
So no one care this.

如果是元素的話應該是鎢
The chemical element with the highest melting point is tungsten, at 3695 K (3422 °C, 6192 °F) making it excellent for use as filaments in light bulbs. The often-cited carbon does not melt at ambient pressure but sublimates at about 4000 K; a liquid phase only exists above pressures of 10 MPa and estimated 4300–4700 K. Tantalum hafnium carbide (Ta4HfC5) is a refractory compound with a very high melting point of 4488 K (4215 °C, 7619 °F).