Iolaus silarus, the straight-line sapphire, is a butterfly of the family Lycaenidae.

It is found in Mozambique, Zimbabwe, Botswana, Namibia, Malawi, Zambia, southern Zaire, Tanzania, south-western Kenya and South Africa.

In South Africa it is found in wooded savannah in northern KwaZulu-Natal and in savannah from Eswatini to Mpumalanga, Limpopo and North West.

It is also present in Afromontane forest on the Wolkberg and the northern Drakensberg.

Adults are on wing year round in warmer areas and from September to January in the cooler western part of its range.