Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Nuveen Small-Cap Value Opps R6 (NSCFX): 0.81% expense ratio and 0.8% management fee. NSCFX is a Small Cap Value fund, and these funds are known for investing in companies with market caps under $2 billion. NSCFX has achieved five-year annual returns of an astounding 10.88%.

T. Rowe Price Science & Technology Fund (PRSCX) is a stand out amongst its peers. PRSCX is part of the Sector - Tech mutual fund category that invests in technology and lets investors own a stake in a notoriously volatile sector, but with a much more diversified approach. With five-year annualized performance of 12.07%, expense ratio of 0.8% and management fee of 0.63%, this diversified fund is an attractive buy with a strong history of performance.

Franklin Global Equity A (CFIPX Quick QuoteCFIPX - Free Report) is an attractive large-cap allocation. CFIPX is a part of the Non US - Equity fund category, many of which will focus across all cap levels, and will typically allocate their investments between emerging and developed markets. CFIPX has an expense ratio of 1.22%, management fee of 0.75%, and annual returns of 14.53% over the past five years.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.