30 years, voters in the tiny but strategically placed Horn of Africa country will have a choice of Guelleh or his lone challenger, former Constitutional Council head Mohamed Warsama
Ragueh, when polls open at 6:00 am (0300 GMT).
The main opposition Union for Democratic Change and Union of Democratic Movements are boycotting after they failed to find a joint candidate and because they dispute the independence
of the election authority.
They have also slammed parliament's decision last year to change the constitution to enable 63-year-old Guelleh to run for
a third term after being in power since 1999.
The ex-French colony, home to the only US military base in Africa, was rocked in February by its largest street protests since independence in 1977 when thousands of youths took to the streets demanding Guelleh, "the dictator", quit.
The demonstrations which came as the Arab world was gripped by a wave of uprisings against veteran rulers degenerated into violent clashes with security forces that left at least two people dead, according to officials.
They came a week after protests toppled Egypt's long-time leader Hosni Mubarak on February 11, with Tunisia's leader falling in a similar revolt the previous month.