the Arab Republic of Egypt, which alone continued to use the name UAR from 1961 to 1972, see Egypt
However, between 1961 and 1972 United Arab Republic was also the name of several Arab nationalist attempts to restore the old UAR, to establish a new UAR or to unite with the UAR (i.e. Egypt), for example
the Tripartite Unity Talks (1963) between Egypt, Iraq and Syria which failed after ba'athist-nasserist clashes in Syria
the Union of Arab Republics which Iraq proposed in 1972 as a restored UAR with Egypt and Syria. (It failed because of the earlier creation of the Egypt-Libyan-Syrian Federation of Arab Republics.)
the United Arab Republic which Egypt and Libya planned 1972 as a more substantial union within the Egypt-Libyan-Syrian Federation of Arab Republics.