Arsenal have agreed a deal with Valencia worth an initial £13m plus add-ons for defender Cristhian Mosquera.
Personal terms on a five-year deal have also been agreed in principle.
The 21-year-old is expected to fly into the UK in the next 24-48 hours for a medical and to finalise the move.
Arsenal are hopeful all will be sorted in time for Mosquera to be part of the squad that flies out to Asia for the club's pre-season tour on Saturday.
Mosquera has effectively confirmed his departure from Valencia. "This is my home and it always will be," he told Spanish radio station Radio Marca Valencia.
"I arrived here at 12 years old and I'm leaving as a man. I'm a bit sad."
Mosquera was born to Colombian parents in Spain and joined Valencia at the age of 12, going on to make 90 senior appearances and scoring one goal.
He has also made 11 appearances Spain U21s, starting all of their games at this summer's U21 European Championship before they were knocked out by England in the quarter-finals.
Mosquera is a naturally right-sided centre-back but has also played on the left and is expected to provide competition for both William Saliba and Gabriel Magalhaes.
Arsenal spending to pass £200m?
Mosquera is set to become Arsenal's fourth signing of a busy summer, following the additions of goalkeeper Kepa Arrizabalaga and midfielders Martin Zubimendi and Christian Norgaard.
Arsenal are also close to agreeing a deal worth around £64m for Sporting striker Viktor Gyokeres, while winger Noni Madueke has had a medical ahead of a £52m move from Chelsea.
Those signings, together with that of Mosquera, would take Arsenal's summer spend past £200m.
In
Kepa Arrizabalaga - Chelsea, £5m
Martin Zubimendi - Real Sociedad, £51m
Christian Norgaard - Brentford, £15m
Out
Jorginho - Flamengo, free
Kieran Tierney - Celtic, free
Nuno Taveres - Lazio, £4.3m
Marquinhos - Cruzeiro, undisclosed
Takehiro Tomiyasu - released
Thomas Partey - released
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