The three nations announced their collaborative bid at a media conference at UEFA's headquarters in Nyon on Wednesday.
The Royal Spanish Football Federation said: "The RFEF and the Portuguese Football Federation (FPF) have incorporated the Ukrainian Football Association (UAF) into the Iberian Bid to organize the 2030 World Cup.
"The proposal has the unconditional support of UEFA in a global project and transformer of European football in an exceptional situation.
"(RFEF president) Luis Rubiales and (FPF president and UEFA vice-president) Fernando Gomes understand that there is nothing better than a World Cup to strongly transmit a message that will serve as a source of inspiration in the future."
The 2030 World Cup will be a 48-team tournament with the finals set to be expanded for the first time at the 2026 edition, which will be hosted by the USA, Canada and Mexico.
It has been reported that Ukraine intends to host one of the groups if their joint bid is successful.
Spain, Portugal and Ukraine face stiff competition from other 2030 World Cup bids, which include a four-nation South American proposal from Uruguay, Argentina, Chile and Paraguay.
Another three-nation bid from Saudi Arabia, Egypt and Greece is expected and in 2018 Morocco confirmed they will bid for the 2030 World Cup in a possible joint-venture with Tunisia and Algeria.
RFEF president Rubiales added: "It is no longer the Iberian bid, now it is the European bid.
"Fernando and I, in Portugal and in Spain, see how friends and families host tens of thousands of (Ukrainian) exiles, who are currently outside their country.
"I am convinced that these boys and girls will remember this historical moment for them. And they will grow up with the hope, which is a precious word, that one day that moment of peace will come.
"If football can help anything, even if it's one per cent, we're satisfied."